how does dockx maintain stacks, does it set custom xprop hints on windows ?
It matches by application, and (depending on the settings,) normally ignores windows on other workspaces.
https://github.com/ValveSoftware/steam-for-linux/issues/1040 implementing that would probably fix this issue.
My window manager (dockx,) lets me close all windows in a stack, if two windows of the same application are on different work spaces they're in different stack and therefore closing all windows on one stack won't close the other windows..
If I have steam on workspace 4, and a steam chat window or multiple chat windows on workspace one, choosing to close all windows in the stack of steam chat windows, will shut steam down, even though steam its self is on another workspace.
Minor usability problem.