You didn't say what breed(s) you were looking for, but there's some here, here and here. If there's another type of breed you're looking for, using one or some of those as a base might work rather than making one completely from scratch
im on the same page as Elaine, i mainly just use sliders from around the community i think the main one i cant live without is the neck base/wither height slider which can be found here. I use it on most if not all my horses
You can also find a heap more for whatever suits your style here on the CC Database
And thank you very much for the compliment, it means a lot!