Hi!
It was me who responded the other time
You are mistaken. The Shift key has nothing to do with supply situation.
To see the supply layer you must press the appropriate button on the interface: left bottom, over the minimap. Its the second from the left.
Shift key has two uses:
- one, show the movement connections between adjacent regions, as i told you before. The colors identify the different kind of connection between the region the selected unit is and all the adjacent ones (railroad, road, cross country, river crossing, mayor river crossing, sea...
- The other works only when you have selected an Army HQ stack. Then, pressing shift will show you a blue/grey colored area (depends if you play with the USA or the CSA) which is the Army command radius.
Any other stack with a two star leader inside this colored area is eligible to be a Corps of that army. And the corps which remain inside the radius will recieve bones/penalties from the Army HQ leader.
You have a full short keys list on the page 50 of the manual
Hope its clearer now.
Regards!