I’ve done a few hacks to GNOME tools, filed below.
Gnome-terminal
A common terminal action is copy copy and then paste text. If you have three mouse buttons, the middle button does this action. If not, it’s two painful steps. (Yes, you can emulate three buttons, but that has problems of its own.)
Other applications have a “duplicate” menu choice. Gnome-terminal should have this choice too.
This patch adds a duplicate action to gnome-terminal-2.7.3.