Perhaps you are using the “Quick Settings Docker” until your feature request is implemented, or perhaps you are placing another “Brush Options Slider” for flow in the toolbar. To do so, you use the small triangle on its left-hand side to expand the drop-down menu and the plus sign on the right-hand side of the flow slider to place it in the toolbar (as you can see it in my screenshot). And do you use this slider as a substitute as long as nothing better exists?
I don’t know your workflow, but perhaps it could be useful to use @kaichi1342’s plugin “Compact Brush Toggler,” which offers the possibility to switch Flow (and some options more) on and off whenever you need it. I hope it is not broken through one of Krita’s recent updates.
Link to its topic here on KA:
and link to its Github-Page:
Michelist
Edit: Punctuation