Honestly, it’s a limitation on an application level. In theory, you could create a masterkey file out of the recovery key. So if you really only have the recovery key and lost your masterkey file, you could do the following workaround:
- Create a new vault.
- Copy masterkey file from new vault to old vault that has a missing masterkey file.
- Select old vault in Cryptomator.
- Go to “Vault Options” and select “Password”.
- Select “Recover Password”.
- Use the recovery key.
- Assign a new password.
Edit: You should only use this workaround if you are absolutely sure that your vault contents match the latest vault version. If you recover a masterkey file via this method and your vault contents actually match an older vault version, the new masterkey file won’t necessarily “fit” the vault contents.