Sorry for the HUGE images :D but i had to make sure you see everything :( (and i was too lazy to do another 7 pics with zoomed view so DEAL WITH IT Lolz)
First step open map go to start location,expo that you wanna move minerals for:
Go to Copy/Cut/Paste/Brush Layer and uncheck everything except for "Units"
Select and Copy the minerals and gas WHILE IN THIS LAYER! don't change it to UNITS one very important ! ;D
Now after you copyed the resourses and expo go to the Units layer and Select the old mineral line
And DELETE it =D
Go back to the Cut/Copy/Paste/Brush Layer and place your new mineral line
And here is a simple method to check if if it works:
RIGHT
WRONG
(You can check the gas too by taking a new gas and placing on top of the other one, if they blend and are in the same spot then it works, if you see 2 gaysers then i dosen't)