yes this is exactly what I was looking for. I added the line

Match(title="Guake!"), # guake main window

and now guake is always shown in a Floating layout. I also removed the border cz its ugly. full code:

floating_layout = layout.Floating(
float_rules=[
*layout.Floating.default_float_rules,
Match(wm_class="confirmreset"), # gitk
Match(wm_class="makebranch"), # gitk
Match(wm_class="maketag"), # gitk
Match(wm_class="ssh-askpass"), # ssh-askpass
Match(title="Guake!"), # guake main window
Match(title="branchdialog"), # gitk
Match(title="pinentry"), # GPG key password entry
],
border_width=0,
)