This value was thresholded in the previous stage.
If this is an accepted neologism in your current context (e.g. at your company), and the document which contains this sentence is intended for people who work at your company, then you can simply use the neologism.
Localized definitions can override general English definitions, as long as you observe the correct context (i.e. one where the localized definition applies).
I would suggest adding a small dictionary to the document; which further explains the meaning of "thresholding". However, that is a matter of good practice and work ethic, which goes beyond the scope of English.SE.
However, if you are communicating something to a larger context (e.g. people who do not work at your company), then I would suggest finding alternatives. I'll list a few I can think of.
Truncated, as mentioned in another answer, is a good alternative. However, it is not the value that is truncated, but the list of values.
This value was truncated in the previous stage. (wrong)
The list of values was truncated in the previous stage (right)
Trimmed is similar to truncated. It is an established term in programming; but its figurative use should be understandable without any specific technical knowledge.
The same rule applies as with "truncated": It is the list that is trimmed, not the value itself.
The list of values was trimmed in the previous stage.
Continuing with the figurative description of "trimming a list", pruned would also work. While technically correct, I am not a big fan of this option. It sounds just a bit too contrived, and it distracts from the actual topic of conversation.
The list of values was pruned in the previous stage.
Omitted also works. It means that you have intentionally dropped these values and will no longer refer to them.
This value was omitted in the previous stage.
However, it could possible mean that this value was omitted only for this specific stage, which is not the case for you. So I would suggest phrasing it differently, to prevent this ambiguity:
This value has been omitted since the previous stage.
This alternate phrasing makes sure to convey that the omission of this value is permanent, not temporary.