if not, will using multiple schemes of, say, a golem, make construction cheaper? or perhaps make more resources or last longer?

Golem schemes do not stack unfortunately.

Building schemes do stack. Use five to reduce the money for the building each time.

If yoou use a scheme it disappears from inventory and opens in your Craft and Constrauction tab.

Thank you so much for replying! Just to clarify, if I use a scheme, it stays in my crafting menu and I don't have to get another scheme to make another of the same item?

Ok, to simplify:

Use a scheme to send it to Craft and Construction.

Items and golems: only one scheme needed.

Buildings: up to five schemes to lower the amount of silver required to build it each time.

(Golems disappear in Crafting menu while they are active and reappear afterwards)

(Tundra specific items are only visible and craftable during tundra)

Okay, I think I understand. Thanks a ton!!!

Pleasure!