TL;DR I need to make Cura start printing each of four models at the purge tower for only one layer.
I'm printing gridlines that need to be all white except for particular color details on ONLY the top layer of the gridlines. To accomplish this I have created 3 more stls of each detail that are one layer thick and aligned them where they need to be in relation to the main board. This makes it so some of this top layer will be the first white of the main board and other parts of the layer will be different colors according to the three details. Nothing that is being printed overlaps. I'm using an Ender 3 V2 with no modifications (single extruder).
I've accomplished this on a single layer with only two colors, as I have found that Cura will complete one model in a given layer before moving on to the next model. I have made this work by adding a Pause at Height post-process to the layer in Cura and then manually cutting and pasting it in the gcode to go right before the new model starts instead of at the beginning of the layer (with a couple edits to the extrusion code).
My problem is that I want to have a little purge tower to prime the nozzle for each color (I have found this necessary for it to start extruding cleanly when it moves to my target model, even after I have purged it during the pause). I've added a portion of the purge tower to each detail STL. Cura starts printing the first subsequent model all the way at left edge of the board, and that has made it so I can place my purge tower where it will start printing. But I have found that with more than two models, Cura will still print them one at a time, but will start printing each wherever is closest to ending the previous model, and not at my tower (sometimes it prints its portion of the tower at the end of the new color.... Not very helpful...).
How can I make Cura start printing each model in this layer at my purge tower? I've never used any other slicer. Are there others out there that can allow me to tell it where to start each model in a layer?