I'm afraid you need to use the SD card. Some functions of M+ require the use of the card (which has hidden partition/files/folders or whatever).
I dont know how to sort out your problem. I personally use only a couple expansions so plenty of space on my SD card
All NI content must be installled on the SD card through the install process. There’s no other way.
Get a good quality full size SD card. 512 GB should be sufficient for everything. My 256 GB has about 100 GB left and carries all M+ content, all Expansions included with KUCE 14 and a couple of GB custom samples.