By default UGENE supports Genbank file modification only if a file was initially created in UGENE.

The reasons of the limitation are: avoid data loss for sections with non-standard formatting and do not favor modifications of files obtained from official sources (e.g.Genbank database).

Method 1

A Genbank file can be modified by UGENE if the header section of the file contains a special tag: UNIMARK <annotation table object name>

Add this tag to the header of your Genbank file with any text editor to make the file editable by UGENE.