On Windows you can create a symbolic link for now until a “true” solution comes along.
Search Programs and Files > cmd
mklink c:\users\username\documents\unreal projects d:\Users\username\documents\unreal projects
This will create symbolic link between the two folders and you will still access your projects via the C drive documents folder but all of your projects and saves will be stored on your D drive.
If you are finding that you are in a constant state of always having to make room on your SSD then it’s time to upgrade as the primary drive is sill used to create a lot of different temporary files as well is used for page swapping, unless you change what drive is used for the swap file, and if you find yourself with less than 20% of the total drive space left you will start to run into performance issues.