I find the “search by chords” tool great to consult when writing music, but it would be really useful if you could also search for sus chords. For example, V/vi is often preceded by iii or by iii sus4, but it’s difficult to tell from “search by chords” which one is more common because the iii sus4 chords are lumped together with the iii chords. This is further complicated by the fact that iii sus4 could also be entered as III sus4, so even if you search for iii - V/vi and go through all the songs one-by-one counting how many are actually iii sus4 - V/vi, you’re still none the wiser because you’ve missed all the songs where the chord has been entered as III sus4. In fact, there’s no possible way of searching for a III sus4 - V/vi progression in “search by chords” – the III sus4 chord isn’t counted as iii, and III doesn’t appear as an option, so you can only find the chord as V/vi, but you (quite sensibly) can’t search for a V/vi - V/vi progression.
I could understand lumping sus chords together with the corresponding major or minor chord if this were also done for 7th chords, secondary dominants, borrowed chords, inversions etc., but it’s not. “Search by chords” offers the choice of iii7, V/vi, V7/vi, bIII, iii6, iii6 4 and iii6 5 but not iii sus4 or iii sus2. It would be better if iii sus4 and III sus4 were both counted together – after all, they’re exactly the same chord – and not as iii and V/vi respectively.