In Version 0.21 there stand at in geany with german Strings Bearbeiten -> Einstellungen -> Terminal a CheckBox called "Menütastenkombination deaktivieren (Vorgabe ist F10)". The "n" in "Menü" is underlined.
And in the current GitHub-Version there is nothing underlined, but there stand "Me_nütastenkombination deaktivieren (Vorgabe ist F10)"
Hope it will be fixed before the release of 1.22.
Greatings theuserbl