@sebkritikel when I said "a standard i3 printer" I meant a regular i3 printer shape (a la Ender 3, Prusa Mk4, etc), and not and IDEX printer.
I was trying to add the functionality of an IDEX's duplication/clone mode to a non-IDEX printer. I built the printer with two X-axis carriages on two linear bearing blocks, on a shared MGN15 rail, driven by a single X-axis motor. Each carriage has a clamp on the top that grabs onto the belt, so they are easy to reposition quickly.
The idea behind the macros is that right now, returning to "regular" dual extrusion is going to be inaccurate since my existing carriages weren't really intended for this, so they can't index off of each other accurately, but this is a function that I specifically want to include in the "final" version of my printer - I already knew I needed to re-design my X-axis carriages to make them more modular, but this definitely added some ideas for features that needed to be included to make this kind of function-change easier.
The Macros make it easier to reposition the heads on the belt that drives both carriages, and once the carriages are re-designed to include the added features I thought of, it'll be both more-automatic and more precise, but still require a little manual intervention.
The printer running: https://www.instagram.com/p/CxvR9s2gZuV/ (it's a 350x350x500mm build volume, Orbiter V1.5 extruders and Dragon HF hot ends, with a BL touch). I'm planning to replace the BL touch with a simple micro switch, add a DUEX board, and move to a part of Volcano Chimeras running in bowden mode, possibly still using Orbiter's, but more likely a BMG clone.
Thanks for the info on defining a third tool - I will be playing around with that and see how I like it compared to the way it's running now.
