Double Selection

[tuxii]

Sometimes in my secret underground lab testing I want to be able to select two items rather than be just limited to one.  This would be helpful for when I want to monitor two things at once. For example, a Pacu and a Timer Sensor where I want to dial in the algae rations through a Timer-controlled Conveyor Chute.

The secondary selection could be activated with Shift-M1. If nothing is selected it would select as normal.  If something is already selected the Shift-M1 would close any building menu currently open and show the second selected item on the left side of the screen.  Opening any building menu automatically deselects the left side selection.