Board management vs custom fields

[alorenz]

I can't find a straightforward solution for the following scenario (which should be pretty common) -- am I missing something?

* I'm coordinating a small team in Trello: I maintain the data for 100-200 small tasks -- locations, appointments, what needs to be done etc

* About 70% of those tasks I do on my own, 30% with various team members

* Team members should be able to see only the "team jobs" (i.e. those latter 30%, ideally only those that they are personally assigned to)

* They only need to see the data, not change or edit anything

* Each task has an estimated completion time (hours per person)

I currently have a "main" Trello board for 100% of the tasks, and a separate "team board" where I copy over the "team job" cards via Butler. Not ideal since it creates redundant data, but OK-ish as nobody (except me) can mess up data even by accident .. the team isn't all Trello power users and I don't expect them to be.

--

Now I would like to upgrade to Premium to achieve two things:

* Get rid of all the duplicate data and use mirror cards (or something to that effect) instead

* Implement a simple overview of total time estimated, in all cards, ideally sortable/viewable by list or by month or something.

I thought this would be easy -- simply throw in a few custom fields and sum them up -- but right now it looks like a catch-22:

* either I use mirrored cards, then I cannot access the custom fields in the mirrors

* or I sum up time in the original cards only -- but then I need to live with my clunky Butler copies forever.

For the time overview, I've looked at the Sums, Costello and SumUp power-ups (Sums looks like the best solution right now), so that part is covered. But I don't want to maintain umpteen copies of the same cards forever .. particularly since I've already managed to edit copies instead of originals more than once, and right now I have only *one* team bord which may change in the future.

So, what is the Trello way to do this? How can I provide read-only access to a *subset* of cards, while still being able to access custom fields in all cards myself?

I don't care whether that subset is defined by list, board, label, member or anything else. But I need to reliably restrict access to everything else -- giving the entire team access to all data is not an option.

[Theodoro Reato]

Hi there

Mirrored Cards and Custom Fields: There are no limitations regarding Custom Fields when using mirrored cards in Trello. When you mirror a card from one board to another, the card itself still "lives" on the original board, and any Custom Field values is added to the original card and can be seen on both boards. You can update Custom Fields from either side, and the changes will be reflected everywhere the card is mirrored. This means you can safely use Custom Fields with mirrored cards to track your estimated completion times.

For your use case, you could set up a simple automation: when a task involves one of your team members (the 30%), you mirror the card to the team board. This way, team members only see the cards relevant to them, without duplicating data or risking edits to the originals.

Time Tracking: Currently, Trello does not have a built-in feature for tracking time spent on cards or tasks. Using Custom Fields for estimated hours, as you’ve done, is the recommended approach. However, as you mentioned, this can become complex if you need detailed reporting or live calculations.

As for Power-Ups like Sums, Costello, and SumUp: since these are third-party solutions, we unfortunately can’t offer support or recommendations regarding their setup or capabilities. If you choose to use them, it’s best to test them thoroughly to ensure they meet your needs.

Access Control: Trello does not currently support restricting visibility of specific cards within a single board, access is always to the full board. The best way to provide read-only access to a subset of tasks is to use a separate team board for these tasks. You can invite your team members as Observers to this board. Observers can view the cards but cannot make any changes.

I hope this helps!

[alorenz]

Thanks for your answer.

You write

"For your use case, you could set up a simple automation: when a task involves one of your team members (the 30%), you mirror the card to the team board. This way, team members only see the cards relevant to them, without duplicating data or risking edits to the originals"

That's exactly what I was trying to do --  but that did not work because my team members can NOT see the mirrored cards. We tested this right away. They sent me a screenshot that shows the mirror cards on their board saying "this card is mirrored from a board that you cannot access" and an "request access" button. (Translation mine, their Trello isn't in English).

See screenshot -- the three in the middle are mirrored cards, the rest are those manual Butler copies.

Is this how it's supposed to be or not?

--

When I tried it the other way around -- creating the "team cards" on the team board and mirroring to mine -- I ran into the custom fields problem I mentioned. I can see and edit the custom fields all right, but I cannot track them -- meaning I cannot use any power up, not even Dashcards, to sum up the values in those fields.

You write "There are no limitations regarding Custom Fields when using mirrored cards in Trello" ... "This means you can safely use Custom Fields with mirrored cards to track your estimated completion times."

Dashcards is not a third-party thing, so that should work even if all else fails, right?

I just tested this again:

- the card "Test" lives on the team board (blue) and is mirrored to mine (green). custom field "AT 2P" has a value of 10.

- the next card (with the completion date) lives on the green board, custom field "AT 2P" has a value of 1. That is the only card in this list that has this field set.

- the dashcard is supposed to be tracking the sum, but it doesnt. All it sees is the value in the second card (and all other cards in this list, if I put something in that field), but not in the mirrored one.

Here's the settings in the dashcard > Explore and edit:

It only lists one card with "AT 2P", although two (one original and one mirrored) have that value set.

Is it clearer now what the problem is?

The third party plugins behave exactly the same .. they work fine for non-mirrored cards but not for the mirrored ones. So it doesnt seem to be a Dashcards-specific issue.

[alorenz]

Oh, I believe I see the mistake I made with the tracking stuff ...

It is tracking only cards *on the same board as the dashcard*, and THAT is why the mirror cards fall through the cracks. The mirrored card isn't on the same board, only the mirror is. Duh.

When I remove that board filter, it starts tracking a bunch of stuff (duplicates from testing I suppose) -- but the mirrored card is being tracked now, and tracked only once, that is what matters.

"List is one of "same as dashcard"" apparently doesn't mean what it says -- it's talking about the list *name*, not the actual list. So better not have a "2026-Q1" list on every board ...

So to update my mental concept: mirrored cards aren't "equal" -- there is still an original->copy relationship (the difference is just that changes to the copy will update the original).

Leaving this here for others who run into the same issue.

Still curious as to whether observers are supposed to be seeing the mirrors *from* the private *to* the team board (first question).

[Theodoro Reato]

Hi there,

Thank you for sharing more details about your workflow.

Regarding your request, there was a feature suggestion to support this functionality: https://jira.atlassian.com/browse/TRELLO-980. Unfortunately, this feature will not be implemented, so it isn’t possible to achieve the workflow you described natively in Trello.

With Dashcards, you can select other boards that must have the Power-Up enabled, and from the main board, you can gather statistics from the team board. 

At this time, your options are to use a third-party Power-Ups for mirroring, or to manually copy cards between boards, or to create them in the teams board and mirror to your main board. You could also consider using Automation to help with some tasks, for example, searching for a card by name, archiving it, and then copying updated information to the relevant board. However, please note that automation can only update certain fields and may not cover all your needs.

[alorenz]

Automation is what I'm already using on the Free plan -- that is how I'm currently populating the team board in the first place. 

Getting rid of that (by mirroring the cards instead) was what I was hoping to acheive with the upgrade. Ah well.

I suppose I'll settle for keeping the current method (redundant copies) and use the Sums power-up for my calculations. That looks to be a lot more straightforward than having to maintain separate Dashcards for every list and every field .. and above all, having to keep track of all of the list names.

Still, thanks for your honest answer -- saves me time with testing and setting things up. Cheers!

[Theodoro Reato]

Apologies for not having a direct solution.

Have a great day!