You probably won't get any help here with regards to creating a UX.
I have asked similar questions over the years on different places around the web trying to learn different things and found it rare that anyone will help.
As advised above being able to program, or at least have an understand the programming language used is a big advantage.
I know nothing about writing programs and very little about programming languages, but had some success over the years by modifying what other people have created to suit my needs.

I don't understand how UX's are created from scratch, to me they appear to be mostly a separate file that a setting or settings are contained in, that doesn't require the hassle of modifying the program or skin config files or code to make them work, and that opinion may not be correct.

I have managed to modify some iGO8 and Primo programs and skins by experimenting with much trial and error and a lot of time consumed doing so, and even after years of trying there are still what I believe are very simple things I cannot figure out.
Like changing the colour of an offroad navigation straight line that's displayed from current location to the destination, that I know can be modded as they were created a certain colour, but can't figure out how changing that colour is done.

If I had to start again I'd probably start with a copy of a simple UX and try modifying different things in it and see what the results were.

I started by learning to modify a skin for iGO8, the Dimka_1147 skin and that was to change the linear compass's appearance which was simply a matter of changing the image used for it's display...or so I thought
Turns out it wasn't quite that simple, a certain type of .bmp image is required, that may or may not be a transparent .bmp, then there was modifying the skin.zip file without breaking it, simply unzipping, replacing the image and re-zipping didn't work, and for the modded image to show correctly on all screens in the program it was displayed it had to be changed in the skin.zip and the program's data.zip.
And I found the more I wanted to change, the more complicated it got.

It's possible some changes require mods of the UX, the skin files and the program's files to be successful.
I guess the same may apply to creating some UX's, there may need to be changes in the skin in use and the program to get it to work correctly.

Good luck!