Which Trello add-ons (called Power-Ups) are useful for tracking how much time people spend on tasks and for managing team workloads in projects?
For tracking how much time people spend on tasks and for managing team workloads effectively within Trello you can definitely use Planyway. It covers it all in one app.
As for time tracking, Planyway offers integrated time tracking directly on your Trello cards, plus list and calendar view tracking in-app. Team members can start and stop timers, log their hours, and you can see aggregated time spent per task, per person, or per board in reports and compare tracked time with estimates.
As for workload management, it provides a visual timeline and calendar view where you can see:

You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.