I'm trying to configure my own ore veins to be like the ones found in /data/minecraft/worldgen/noise_settings/overworld.json (the granite/tuff copper/iron ones) but I'm running into an issue where I'm unable to get the rarity of the veins right. I've been at this for a long time now but due to the sheer amount of buttons and dials that appear to do very similar things, I'm unable to get the result I'm after. Do you have any recommendations for things I could try to get large natural veins to appear very rarily? I want like maybe a single vein (out of roughly 20 ore types) every 10x10 block of chunks.

I did manage to figure out that I can use rarity_filter, but I can't seem to find any good documentation on its behaviour, especially for very large or small values.

After much toiling, I have finally figured it out.

"toggle" can be seen as a function that returns a value that then gets filtered by the bottom part of the toggle block. xz_scale and y_scale are used to change the density of the veins it can come up with. Values range from negative to positive, with positive values being smaller veins.
One can then use the filter portion of the toggle block to filter out veins that are too big or too small. After a vein was selected, it gets filtered for whether or not the right Y value was picked.

From there, the ridged portion is for shaping, which again uses density as a constructor, but probably in some different way. I haven't messed with changing the shape of veins, I only just understood how to influence their rarity and size. This section is also where you define which blocks appear in a vein, and optionally where you define the ratio of other blocks to ores for this vein.

I hope someone else comes across this thread so that they do not have to toil with this system for nearly as long as I did.