If you use the Flameshot screenshot capture and annotation utility, you might have noticed that the Choose an app to open the capture (or Ctrl-O) option doesn't work right: something flashes quickly on the screen but nothing happens.

That's Flameshot throwing a fit because it can't open a popup window with the size it wants in i3. So to make this option work, let it 🙂

Add this line to your .config/i3/config:

for_window [class="flameshot"] floating enable

As a bonus, it also makes the configuration screen look better.