If you have marked one or more lines at one side of the difference display then this command pastes lines from the clipboard into the marked area. The “Undo” menu function reverses this action. The “Save Modifications” command then actually stores the lines in the corresponding text file.
Paste is available in text file comparisons only, and only where the side may
be written — Merging Changes lists the cases in
which the command is greyed out, from archive entries to a side locked with
/read-only.