It is the "final stable build." And it is, in many ways, a masterpiece of brittle engineering.
The patch notes, if you can find them archived on a dead Discord link, read like a fever dream: frosty mod manager 1.0.6.3
: Users have frequently reported that the "Launch Options" tab is missing in version 1.0.6.3. This feature was reportedly removed or modified because it was considered buggy. It is the "final stable build