This is basically a remake of phineasjw's Replicator Bed Level Jig in OpenSCAD. It's not as fancy, because my patience with OpenSCAD ran out, but it does work.
My dial gauge was too short for the original. With this one you can make a custom jig that suits your dial gauge diameter and length. You can also customise holes for the magnets.
The variable dial_gauge_z sets the distance between the top of the milled rods, to the top of the beam where the dial gauge rests. The attached STL is at 15mm. If you go much lower, you may need to play around with the filleting.
For printing and usage, see the excellent instructions at