One of the things that bugged me for a long time in my workflow is that I sometimes forget that I have something running in another activity, and then get surprised that after a reboot, I have a couple vim swap files and similar.
At first, I was planning to add a simplified visual representation of active windows to the activity switcher similar to what the desktop pager does.
After some discussions, we realized that, while it may look cool, it would add unnecessary visual noise to an already information-filled space.
Instead, I decided to go for something simpler. The main information is whether there are any windows in an activity, not the count, and especially not their locations on the screen.
And here it goes: