Adding Instrument

Hi Guys,
Happy New Year.
In MuseScore 2 and MuseScore 3 I added a "Flute d' amore" in B flat to the Instrument XML file and was able to use this instrument from a second instrument list. I did this by copying the Concert Flute in C section and then changing the relevant attributes and then saving the resultant XML file in the Documents Folder.
I have tried to do the same for MuseScore 4 but with no success. Can you let me know how to do this?
I don't want to change the standard Instrument XML file unless there is no alternative.
Regards,
Greg Gower