Landscape has too many materials.

I made a landscape material for a landscape that has 28 different materials I want to use on it. But now every time I save the material (After making a change) it takes 1 hour to actually save and I can actually only use 23 layers. (After 23 it crashes). Is there an easier way than to blend 27 materials in one material or to split up my landscape into smaller parts with only some materials?

Full material:

“Sub-materials”: