I haven't tried this... but Pocketbase is opinionated in how it's schema is structured - and it needs to be the tool managing your schema.
Therefore if it was me, I would use the Admin UI to create a new db with a similar data structure, and then use a third-party tool to select data and insert into the new database.
Therefore if it was me, I would use the Admin UI to create a new db with a similar data structure, and then use a third-party tool to select data and insert into the new database.