Could you explain how this differs from BFXR? I like some of the sounds this tool makes but it seems to be missing a few things BFXR has, like choosing the type of waveform for example.
You're right that the tool lacks some features that BFXR has, though not the waveform one specifically (this is the "Mode" slider). Without going too in depth, both tools differ in how they synthesise sound; the goal isn't for sfxia to be a superset of BFXR but to be a tool separate to it that produces sounds that are typically different to what it would produce.