You can create location and group assignments that stay in place through every Guesty sync by adding tags with a prefix in Guesty.
How it works. Add a tag starting with (l) for a location or (g) for a group. For example, (l) Domburg creates a location called "Domburg", and (g) Tiny House creates a group called "Tiny House". The prefix is stripped automatically. If the name matches an existing term on your site, the assignment reconnects to that page.
Why these assignments last. These assignments survive all subsequent syncs because they originate from Guesty rather than being created manually in wp-admin.