I’m sorry, I don’t understand this well:
There are some technical reasons, mostly involving fitting as much as possible into the memory space available, why the pipes are placed into a fixed grid.
You talking about “fixed grid” that we can see in editor (bcs it runs on PC’s resources, I guess)?
Or just structure of code written on Midihub’s chip? I guess it’s not object-programmed then?
Anyway, I need no curves, it all can be all about 90° angle 
Simple table/matrix could be improvement too.
I had “hacked” Midiklik 4x4 before, any setup editing has to be done in text mode, then result was this (for example):
MIDI IN JACK ROUTING (3 port(s) found)
|Jk| Msg Filter | Cable IN 1111111 | Jack OUT 1111111 |
| | Ch Sc Rt Sx | 1234567890123456 | 1234567890123456 |
|1 | X X X X | ................ | XXX |
|2 | X X X X | .X.............. | ... |
|3 | X X X X | ..X............. | ... |
link: How to get a TriThru à la Midisolutions · TheKikGen/USBMidiKliK4x4 Wiki · GitHub [part 9]
Matrix like this could be active and all routing and filtering setup could be done by simple enabling/disabling joint points. This could be less work for you, maybe?
I would like to help but Qt (or any developing tools) is just unknown land for me. I tried to get access for opensource purposes, but it looks like they allow it only for organisations, sad…