Basically I have whatsapp running on a user in grapheneos, would like to transfer my chats/data to another user on the same grapheneos phone. (to segregate it from other apps).

There are few methods, I am trying to avoid the cloud backup way, one way is to scan the QR code, however its not possible to have both apps running in the foreground when switching users.

I could try transferring it to another phone via QR code, and then back again to the correct grapheneos user, however I'm not sure if this would work as the eSIM is still in the grapheneos phone?

There is a "backup" button, but it doesn't seem to create any files in storage? It looks like its for cloud backup only.

Is there a way to create a backup via USB or the file system?

    brando there should be .dbcrypt(version) files in /Android/media/com.whatsapp/WhatsApp/databases (or /backups), so check again. This is where it should also be placed to restore it (there's a good bit of tutorials online).