For the bug reports:

1. While the "Generating Protobases" screen is active (while the program is downloading a quad-feature seedlist to one's system for the first time), the Abort search button is still clickable, and clicking it subsequently disables that button for the entirety of the actual search that follows. If the search is outputting results, enabling the Stop on Results checkbox can halt the program, but otherwise there is no way to stop the program outside of force-quitting the app and reopening it.
2. I mentioned this inside of a Discord server you are in, but in case you didn't see it: the individual octave option for Locate Climate Extreme and the biome map works by setting the nmax parameter of setClimateParaSeed() to the index of the selected octave in either menu. However, that parameter is designed to initialize exactly nmax octaves within the climate, so while the desired octave is indeed initialized, so is every octave that came before it (and thus those are factored into subsequent samples as well). (This can be most easily seen by the fact that the last octave for every climate returns the same output as the full climate itself. ) If this is intended behavior, I feel adding clarification to the two selection menus would be best; otherwise, my personal idea was to replace setClimateParaSeed()'s nmax with a bitarray to specify which octaves should be initialized (which would allow for full customization, and could also be easily implemented in Cubiomes Viewer by setting nmax to 1 << (number of options - selected index)), but for Cubiomes that would require knowing the number of octaves each climate contains in advance, which that library currently doesn't support. Obviously, feel free to fix the bug in whatever way you think is best.

Jereaux also previously found a bug with the getParaDescent function descending in the wrong direction, but given he explicitly pinged you about that in the aforementioned server I am guessing you are probably already aware of that.

In terms of the feature request: it would be useful for me if structure conditions could be set to only test the condition against the theoretical structure seed positions ((i.e. only getStructurePos()) as opposed to also factoring in biomes/terrain as isViableStructurePos() and isViableStructureTerrain() do, similar to how the first half of 48-bit searches function. (I was thinking of using that alongside the custom incremental search range to create lists of structure seeds without receiving duplicates or having to worry about any being disqualified due to the in-game biomes.) I would imagine this would simply require adding another checkbox to the menu (e.g. "Structure seed only") that if enabled returns the result immediately after getStructurePos, but again if you do implement this feel free to do so however you wish.