Is your feature request related to a problem? Please describe.
When creating various schematics, sometimes I want to use different blocks due to either esthetics or just because I have more of X.

Describe the solution you'd like
Upon schematic save, an option to parametrize the schematic. If checked, before saving give a selection via the material list, where I could name certain blocks as ie structural material or windowsill material. Then upon placing such schematic into a world, give a selection for those blocks and the option to replace with any block.

Additional context
Inspired by Factorios parametrized blueprints