This is one of various roots that Tolkien considered for “try”. It first appeared as √NDEB in notes from around 1967, but Tolkien noted that this was “too obviously = endeavor”, and followed this with a new root √RIK “strive”, though √NDEB was not explicitly rejected (PE17/167). In Late Notes on Verb Structure (LVS) from 1969 Tolkien reintroduced a similar root √NDAB “endeavor, try, seek opportunity”, with a verb form Q. nauva “will try” (PE22/151).

Neo-Eldarin: For purposes of Neo-Eldarin, I think √NDAB is problematic in that it collides with other forms like √NDAB “judge” (VT42/34; PE22/154), but √NDEB “try” might still be useful, perhaps with the nuance “*make an attempt, expirement” as opposed to √RIK “strive, *work towards, put forth effort”.