In Rule based Test Scenario an alias in Given/Expect facts for either instance or property can be introduced (i.e. in header cells) and override the default instance/property names.
The header cell can be opened in editing mode by either double-clicking on it or arrow key navigation and pressing Enter.
When the editing mode is opened the changes can be either confirmed (by pressing Enter or Tab) or canceled (by pressing Esc).
When the editing mode is canceled using Esc, any consecutive attempt to edit that exact cell is not successful - the editing mode for the cell can't be opened neither by clicking nor pressing any keys.
For others (not yet hit by the issue) the editing mode opens fine up to the moment described above.
The issue is not present in ordinary cells (the lines for actual test scenario definitions below the header cells of the grid.)
The only workaround is to close and open the editor anew.