Migrating custom pallettes from MuseScore3

I will start with the general support forum to ask my question:

Is there a tutorial on migrating custom pallet items from MuseScore3 to MuseScore4? I had a bunch of custom line types and things that I would like to move, but it took a lot of hard work and uncertain starts before I could create them. Now it looks like I have to go through the same sequence again (which I have forgotten by now) in a new system that probably has new rules...

I have been using version 4 for a couple of months, and like what I see, but so many of these items I have are critical to my work.