Is your feature request related to a problem? Please describe.

There are times when I want to build using only one type of block from the schematic, and the other blocks get in the way, either by literally blocking me from using easy place, or by making it harder to spot missing blocks (I'm currently building a large flat plane made of red and black glass, and it's hard to differentiate between them in the schematic, so I tend to miss some blocks).

Describe the solution you'd like

An option in the "Visuals" tab to disable rendering blocks that are ignored in the material list. For example for my current build, I'd temporarily ignore black glass, and it would instantly be way easier to see if I missed any blocks.

Some kind of system for this is planned. It probably won't work via the material list, because the material list is based on items, not blocks/blockstates.

I would recommend trying a white overlay (possibly with a bit more opacity) for missing blocks, it may be easier to spot and it doesn't blend/distort the colors from colored blocks like the blue overlay.

You can also use the Edit Schematic mode to temporarily remove all except one block from the schematic (using the breakAllExcept hotkey, check the wiki for more information about the edit features).

i can see this being nice when importing a large farm with air gaps that are needed and some that aren't

it'd be nice to have block categories for more generic schematics, for example, if i import a mob spawner farm i want the air inside but the air outside just makes it harder to see and isn't important