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

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.