Beside a standard menu items menu Edit offers several special selection functions:

Select by Numbers... - this will activate Select by Numbers screen to select a rectangle region.

Other functions are:

Select All Cells

Select Vertical Stripes
Select Horizontal Stripes
Select Checkboard

Unselect All Cells

Note:
When more than one cell is selected, Render and Erase functions works over selected cells only. To export selected cells to a file please use Main image popup menu.