+1. This is something that MATE Tweak could improve upon.
I’ve looked at the code, it’s working with files saved to /usr/share/mate-panel/layouts/. It shouldn’t be too difficult to include a folder path like ~/.config/mate-tweak/panels too, and add options to add/remove/import/export user generated layouts.
I’m pressed for time with other projects at the moment, but eventually I hope this feature will make it!