ESC / Return do not work in most dialog box
A very common GUI convention is that when a dialog box appears, pressing Escape closes the window (equivalent to "Cancel"), and pressing Return validates the dialog (equivalent to pressing "OK").
This does not work in dt. For example, after pressing Control-shift-V (copy part of history stack) :
Expected : Escape cancels, Return validates.
Actual: Escape does nothing, Return is equivalent to Space.
A workaround is to use Alt-o (_o_k) / Alt-c (_c_ancel), but 1) this is inconsistent with most other applications, 2) this is locale-dependent, shortcuts will be different with different languages while ESC/Return are universal, 3) some locales do not even have the shortcut (PR to fix this for French locale here for example: https://github.com/darktable-org/darktable/pull/1399).