These are some 3D printable clips to connect 2 cables together. I have constructed them to be similar to the clips Weller uses for their desoldering and fume extraction stations.
The clips are customizable, the default settings work for the cables on the Zhongdi ZD-985 desoldering station. The important parameters are the ones for the cable diameters in Millimeters. I think you might have to reduce the length for very flexible cables.
I printed my clips in PLA, but most other materials should work, too.