Is it normal for the cell values in a Browser Briefcase's grid to not be editable?
Yes. The cell values exported to a browser briefcase are read-only in the briefcase grid.
However, one can edit the "Notes" field at the far-right (right-most) of the grid. In addition, one can export the contents of the cells to a comma-separated value file (CSV) and then edit the CSV.
Please refer to the "Summation Pro Reviewer Guide" for more detail.