If you want to step (deeper) into modular synthesis, Omri Cohen is one of the best teachers for that on YouTube. If you should not know, VCV Rack is a free software version for modular synthesis and there’s an iOS port available called MiRack.
Vital has been updated and now features custom skins amongst other things (For Pro users and subscribers). Vital is a cool wavetable synth for a nice price (80$). Free version available with 75 presets and 25 wavetables.
Francis Preve explains how to use Ableton’s Simpler to create your own wavetables in this article.
This free M4L device made by Dillon Bastan and Carlo Cattano let´s you create custom Wavetables for Ableton´s Wavetable synth from image files. Get it from www.maxforlive.com