Hi Elyptic
We currently don’t allow you to change where Unreal Project’s directory is located. But a trick I use at home is to move location of the “My Documents” folder and Windows will automatically move everything.
I did some quick googling and got a good set of instructions. It’s pretty easy. But I don’t want to be responsible for any data loss so, back things up before moving it 
Your already downloaded content should load correctly from new location.