Hardware (BT) keyboard alternate mappings?

When I associate a physical keyboard via Bluetooth, in the associated settings I see it’s mapped via the default ‘hid-keyboard’, with at the bottom of the dialog a nifty ‘configure kbd layouts’ button, which drives me to… a blank window.
Since my old folding keyboard indeed doesn’t fit the standard config, how can I prepare alternate mappings that would appear there?
Thank you!

OK, coming back some hours later, I found a course on how to build your own keymap here, so if no easier way is available, I should be capable to build my own… but any advice is still intensely welcome :wink: !

Back again: I found what looks like an easy answer, ‘external keyboard helper pro’, with a free demo for testing. Am going to try this evening…

OK. Test done with my old “Think Outside” folding keyboard. That’s a physical-french keyboard that sends QWERTY codes. Before using this app, that is. Now, it seems nothing at all is received.
EVEN once I deinstalled the app, and restarted the FP :frowning:
(…) after a long meandering, it seems one has to not only pair the kbd before but also have it active before launching the app prefs; after that the way to edit is apparemtly effective but quite complex -too complex for me at this time…

I have just tried it with a new rapoo E6100 and External Keyboard Helper Demo. The app installs, the keyboard connects, I can set it to “German”, but the characters that appear when I type are still English keyboard signs. FP1U apparently does not use the changes I set. How to?