Phil Nelson
A&P-IA, Maintenance Instructor
KF 5 Outback, Cont. IO-240
Flying since 2016
One of the easier programs for creating diagrams is Fritzing. It's geared towards PCB design, but easily applicable to what you're trying to do.
https://fritzing.org/learning/
Student Pilot
Here to absorb everything about building a KF.
I've been using Skycad for my wiring diagrams. Here's a low-res snapshot of what it looks like. Fairly large learning curve but easy to make changes.
image (3).jpg
Building SS7
915iS
Garmin G3x