There are moments where you find a good new spot for your existing soldier (for example) and now you just want to move him there (to new better position) - well you can't. You must first find him in game/map and grab him. Meanwhile you lose the position you wanted him to be in and you get angry. So my idea is to just drag anything directly from the left side panel and drop it anywhere you currently are. As simple it is and I don't think it will be anyhow hard to implement it.
If you still don't the idea then look at attached image or click here: