PALETTE HAS DISAPPEARED AND WITH IT - ALL THE CUSTOM ADDITIONS

Can someone please help me. I loaded a lot of basic chord diagrams in the Palette section - each under specific notes e.g. A chords, B chords, Bb chords, slash chords etc and as and when I needed to add another item to the specific chords under the specific headings, for example, Csus2, Gm7(b5) etc - I did so. It has been working amazingly well for a number of months. For some inexplicable reason today, my basic palette disappeared and when I got it back, it was empty. I then closed the palette and thought it would miraculously reappear but alas, it eventually did, BUT, without my precious piano chord diagrams I had painstakingly made. Where would I go to get it back? I even loaded a score that would have had to use the diagrams - but unfortunately that makes no difference. I really don't feel like making these diagrams all over again.

I have obviously gone straight to AppData and Musescore3 and Workspace - it is empty even though I selected to show hidden files. The initial database I worked from (ie the basic chord diagrams) - that was there - but all the custom diagrams I had added to this specific database - is not showing at all.