A few nodes to mix sigmas and a custom scheduler that uses phi, then one using eval() to be able to schedule with custom formulas.
https://github.com/Extraltodeus/sigmas_tools_and_the_golden_scheduler
git clone https://github.com/Extraltodeus/sigmas_tools_and_the_golden_scheduler
comfy node install sigmas_tools_and_the_golden_scheduler