I couldn't find customizable connectors and holders that can be plugged together and extended to various sizes, so I created them myself.
Updated Version, this one can create holders with and without Connectors:
They can be screwed with bolt/nuts together generated with this scad:
I have added some stl files I created using the scad script.
Below the the version history:
/* Version 0.1 - 2020-01-12
- Initial Version created
- Version 0.2 - 2020-01-17
- Added new endtypes
- Added cableholder
- Added rounded corner support using BOSL library