That's not possible. Can I assume this is an image backup? Where are you backing up to? Cloud or local? The new backup format supports synthetic full backups to all clouds (sans Google currently). A synthetic full uses the incremental backup data to construct a new full.

Files backup. Local storage.

which backup format are you using? Are using the legacy format or the new backup format? If using the legacy format then those backups are incremental forever. There's no such thing as a full backup with the legacy backup. All files are backed up with one-to-one correspondence between the file and object storage. If you're using the new backup format then you do need to run periodic fulls, and in the case of local backups currently, there are no synthetic full backups supported yet.