So, I asked in buddiesofbudgie matrix channel how to trigger this dialog:
dbus-send --session --type=method_call --dest=org.buddiesofbudgie.PowerDialog /org/buddiesofbudgie/PowerDialog org.buddiesofbudgie.PowerDialog.Toggle
Now, you need to make a desktop file that runs that command or runs a script that runs that command, then run it via start menu and mark then as favourite in plank