To modulate instrument modulation device params like lfo freq, you can use macro assignments, then modulate the macro from the fx section using a macro doofer (a doofer with and instrument macros device inside, which must be saved from the mixer section, then called up as a preset from within the instrument fx section).
Retarded workflow, I know, but once you get it down, you can do quite a bit with it, and it’s not impossibly slow. You can check out my video tutorials on YouTube under MrZensphere. The very first one deals with this issue.
They’re all also in this thread
•••Zensphere's Renoise Tutorials•••