Invisible - bakkeby/dusk GitHub Wiki
Invisible is an internal flag that is specifically used to hide scratchpads from
view when they are toggled away.
This is similar to that of the Hidden flag except that the window titles of clients
marked as being Invisible are not drawn on the bar.
The flag can be set via client rules if the scratchpad program is to start out as not being visible. One use case for this might be if the scratchpad is set to start automatically with the window manager to shorten load time when you trigger the scratchpad the first time.
Setting the flag for non-scratchpad clients would render them inaccessible.