5 lines of text.
Select from line 2 to 4 by dragging in line number area. (Now the active point is at the start of line 5.)
Use “Join Lines” or “Remove Newline Characters” command.
** I think line 5 should not be joined.
v18.7 ignores the last newline in the selection if it is the last character in the selection, but I need to revert to the original specs because some customer complains the behavior difference. If you really want the new behavior, I will have to make it optional.