This is a small piece that I designed to help manage the wire coming off the build platform on the ThingOMatic. This provides a place to anchor the HBP cable bundle to the right side of the Y-stage. It also acts as a strain relief for the X-axis endstop cable.
This replaces the two 1/8 inch spacers which the X-axis endstop is mounted to. The endstop board mounts as before, on top of this board. You can then use a single zip-tie to anchor the build platform cable and the endstop cable in the channel at the end of the part.
This part assumes you're running the build platform cable through the front right cable hole in the middle plate of your Thingomatic. It would probably also be a good idea to combine this with one of those build platform connector strain relief things.