I had this idea for a mod that would greatly help in building redstone circuits and any other build.
In these 2 pictures you can see an example.
Let's say you want to build this:
You would press some buttons to select an area (or maybe import a schematic) and then you could choose where the overlay would show. This is what it would look like:
If this exists already, I am sorry, but I haven't seen one like this.
It does exist: schematica
Ruins of Humanity (mod): https://www.minecraftforum.net/forums/mapping-and-modding-java-edition/minecraft-mods/wip-mods/2898701-1-12-2-wip-early-alpha-ruins-of-humanity