I have a tab file with 3 columns and I want to join column 2 with 3 and replace the tab between them with : (that is the “:” character and space). I do not see an option to add such a character in the Join dialog.
You can disable Cell Selection Mode (but still keep the CSV (Tab Separated) mode), select column 2 and 3 by (double-)clicking the header or ruler, and then replace TAB with ‘:’ while In the Selection Only option is selected.