I made a web page where you can simulate a complex dice roll sequence with conditionals (e.g. re-roll when roll is a 1) using a Python-like syntax. (Click the "Toggle Syntax" button to view examples)
It needs a second to load because it has to load a Python interpreter in the background (I'm not good at web development) but once that's done, it works really well.
It's still very barebones and I still have to work out some problems.
Maybe some of you could use it, though.
There's also just the Python version available to run locally here
Everything is GPLv3, enjoy!
Heh, I just but one of these for myself, but for the specific "best 2 out of 4d6" the game I'm playing uses. Pretty interesting.
Made me realise that as long as you're free to adjust the success threshold(s), every action dice roll mechanic is basically equivalent (because you can quantile map the threshold to get approximately the same probabilities).
Doesn't hold for damage, I guess.