When uploading a form with the same ID as an existing form, without checking Replace, a copy will be created and the designer will see an error message: "The flow form that was uploaded matches the id of one that already existed so a copy was made. If you intended to replace the existing flowform, delete the flow form you just uploaded and upload it again but check off the ‘Replace’ option."
When uploading a form with Replace checked that is currently being edited by another user, the designer will see this error message: "This flow form is currently being edited by <user@tenant>. Please try again later."
Designer users can grant other users the ability to edit a form and access related submissions. The Access Control and Shared Items topic explains the details. This permission gives Users with this permission also can run the process to Refresh Searchable Fields.