PROBLEM
When attempting to edit a layer containing an annotation feature in ArcMap, the following warning message is returned:
Warning: Could not edit the data in the folder or database you selected.
The issue occurs if the feature dataset contains an annotation feature created in ArcGIS Pro. Feature classes stored in feature datasets containing annotation feature classes created in ArcGIS Pro are read-only in ArcMap, and therefore, cannot be edited. This is a known limitation as described in ArcGIS Pro Web Help: Annotation storage.
To resolve this issue, select one of the options below depending on the ArcGIS platform used:
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