Krita
Fill the selection with the foreground colour
To fill the selection with the foreground colour in Krita, press Shift + Backspace. It is listed for Windows, and no Mac version is documented here.
Where it works: Image open
Where this comes from
Krita default action files - KDE Krita repository
Documentation checked on 2026-09-14. That is a documentation review, not a test run inside the application.