Updated model included to pass multiple cables and has a larger 9mm diameter. It's longer to ease installation and sticks through by about 10mm. The part now aligns to itself with a dovetail feature. The clearance on this feature is about 0.2 mm so that it'll have a slight interference and stay together with a friction fit.
The old design is a two piece plug to drill a hole a seal the cable in place. Part sticks out about 3 mm beyond the bottom of the Lack table surface. No glue required, held in place by hole and gravity. Included FreeCAD files to customize to different cables.
Preparation: Drill a hole using a bit larger than 14 mm, I used a 5/8" bit. I took my time, but still slipped and took a chunk out of the surface.
Print Instructions: Supports needed for floating ends of dovetail design, no supports needed for the old design.
The author marked this model as their own original creation.