The migration is well documented for embedded databases link to wiki.docs, the do you want to migrate question pops up once the box ‘experimental’ has been ticket ( in the tools>options>advanced frame, the one showing the installed JRE )
I couldn’t find an identical procedure for splitted HSQLDB databases.
The question can also be reframed as: how to convert a splitted database into an embedded database. In an embedded database containing one table, I copied the four splitted files, data-script-properties-backup, to the appropriate datafolder with the .odb opened with an archievemanager.
This bypass action is noted by LO 22.214.171.124 (LinuxMint 20) and recovery leads to an empty page.