heyas; you guys do what??? if i have a mixed material, say 'sand' and 'wet sand,' and then i want to add 'grass' to start building a multi-tier terrain material.... i grab the mixed sand&wet sand in the top (main view), then throw it down onto one of the two mixed materials. (grab & throw = click & dragon & drop). this creates a new layer of mixed mixed materials. so then you just edit/load the material you want to mix in with your mix, in the other side.... i think grabbing and throwing down still works, even if you can't unmix by throwing a mixed side up onto the main view. once you mix in the new mix, you can grab it and throw it down to the bottom slot to make another mixture. it's how i made the 'whole mountain' materials. if you're mixing via altitude, remember that the effects are cumulative. so if i had 'sand' and 'wet sand' at 50/50, i might slide that down to like 15%. then mixing the 'sand&wet' with 'grass,' i can put that at like 25%. and when i mix 'grass&sand&wet' with 'rock,' i can set that at 50, and put the snow up at 75. so the wet sand is like the lowest 15% of the whole terrain, et al.