how can I make JIRA look like AtTask?

[Nic Brough -Adaptavist-]

Why?  It's different software, and hacking it to look like something else is a lot of effort for no probably reward.

[Jason Warfe]

Thanks Nic - I don't really want to go thru all of that. I'm more feeling out for suggestions on transitioning from AT to Jira... didn't want to weigh down my inquiry with a lot of nonsense details.

But, I am looking for suggestions on add-ons for waterfall-esque projects. I'm all ears.

[Nic Brough -Adaptavist-]

I'd say define the processes you want to end up with and build workflows that match them in JIRA.  That will give you an end-point, and you can then look at your data in AT and decide what to transfer and how.

I can't recommend add-ons for waterfall - that's far too vague a description of what your process is going to be like.  JIRA's workflows can be Agile or Waterfall, or somewhere between them, or even used for totally different processes, and you define them, so there's a good chance you don't need any add-ons to match your process.