You could also use the Litematica mod, which does work with 1.14 and below. Although with any in-game way to save and paste schematics of your builds, it can/ will cause lag. For me personally, trying to paste a schematic that is TOO big will crash the game (but, my computer is on the older side, and the area that causes crashing is pretty huge). I know there is software that can be used to edit maps outside of the game, but I don't know much about them, or what they're called.
Link to litematica: Here