I also had this problem and actually today i found a solution:

Create a new toolbar button for the command "Rectangular Selection". Afterwards you can change (toggle) permanently to the rectangular selection mode by pressing this button. Then you can place the cursor to the beginning of the selection, press 'shift'+'ctrl' and then 'end' to select a rectangular area to the end of the file. Now you can work with this selection as usual.

To create a new toolbar-button, go to Menu - Utilities - Buffer Options and add the desired button for the command "Rectangular Selection".

I hope this helps.
Hans Bauer