Q: Can you add VRAM to your Mac?

You ere in wrong forum, this is FCPX forum. But you can not ad VRAM, but you can ad RAM, which is totally different Thing.

True, wrong forum.

You CAN add VRAM to some older Macintosh units by upgrading the video card. Newer systems do not have user-swappable cards you maximize your VRAM when you build and order the device at the store.

I have to disagree with you. It is possible to upgrade your graphics card via PCIe to thunderbolt. People have been upgrading the graphics card of the MacBook (Pro's) by attaching an nvidia card via Thunderbolt with a PCIe to Thunderbolt adapter.

https://www.youtube.com/watch?v=uiBFe3yc2Xk&list=PLS-mSvdWal0-nDnraPTyoN1Ll_B4lp Y1L

OP asked if he could install more VRAM, no he can not. Can he install a new graphic card with more VRAM ?, yes, but that is a different thing