Wow this looks incredible! I love the detailed beams with the patterns and the chiselled beams.
This is probably overcomplicating it but I wonder, could a possible mechanic exist where you could use your chisel to make a custom design on a beam and then be able to save and repeat that design with beams? Kind of like the pantograph in QP's chisel tools (https://mods.vintagestory.at/chiseltools), only for beams instead of blocks. The beam hitbox is a cube I think, so perhaps you could chisel a beam design on a regular block, and then be able to convert that design to a beam?
I'll download your mod right away when you upload it!