I've finaly find a way to mount "hos_data" FAT32 partition into Android, usable with all android apps (after 1 week )
You need Root (Magisk), enable "Global Namespace" in Magisk Manager.
After that i use Tasker to mount at startup :
All you need, is to create "Profile" into Tasker, and theses tasks :
You can now share your Roms/Thumbails between Horizon / Android
I hope it can help some peoples ... If people have better solution, without Tasker, please share