You need a tagging rule to tag the CAD files when they're saved.
Thnaks for the reply.
For the moment, I can't set a tagging rule. But with manual tag, I should not need a tagging rule, my tags should stay on the files when they're saved, right ?
No. Look at KB53436. "This also applies to tag preservation. If a tagged file is opened and saved, the tag will be lost if the saved document has less than 350 characters."
If you don't have a tagging rule the tag will get removed.