From command line or from UI?
In case of UI, which URL to access the list of instances to be able to clone (as without repo, app does not show on software center as installed)?
https://<FQDN>/cluster-admin/#/software-center/app-instances/Bookstack ??
Backup
Restore to new instance
In-place Restore
Clone
Clone (with replace option: new instance keeping MODULE_UUID and deletes original one, as intended)