A problem with MEGA-X tool for select the columns of nucleotides and edit them

Hello

I have a problem with MEGA-X tool when I try to edit the columns of nucleotides. In the last version of this tool the user can aligned the nucleotides and then selected some columns of nucleotides with press+hold Shift and selected the columns and then deleted the columns of nucleotides; but in the MEGA-X you can’t use Shit button and select columns. Do you know which button is use instead of Shift to select some columns in this version?