'Lock' tiers in annotation mode

Is it possible to ‘lock’ a tier, i.e., make it impossible to change anything (location on the timeline + values), in annotation mode? In the manual, I only found information on making tiers non-editable in transcription mode. This works, but I was wondering if there is a similar option in annotation mode? I have a tier with annotations imported from a CSV-file and would like to prevent the annotators I hired to make any unwanted changes to those annotations. I cannot make the tier invisible, as it is the parent tier of all the tiers on which my annotators have to create annotations.

unfortunately in the annotation mode it is not possible to lock the visible tiers and their annotations.