Ok, I could be asking in the wrong foru but this seemed like a best fit, so here goes:

I accidentally hit the wrong note in theBig Piano interface, only to really like what I got, but I haven't got a clue what the resulting chord is called:

C-Eb-Gb-B where the C note is the root.

p.s. And before you ask, I no longer have any external thing to make this chord on for the straight forward "Play Current Chord" method, so I haven't found any way to actually enter this chord into the Chord Sheet (since I don't have a name for it!).

If we were friends I'd call it 'mate'.
Otherwise - Cmm7b5
Fun chord on a guitar - Not!
Bests
Ian

Very good, though that wouldn't fly inside BBox when I tried just now, nor would my own wacky "CdimMaj7" suggestion... so I guess this one is not a "fun" one for the program either, much like with your guitar

B/C

...might give you the sound you are looking for - if BIAB will play that...

Ah yes, the trusty "root note" trick, of course!

Interestingly, I've just discovered that (at least for midi) it will not play a slash note on the endings

... something for PG to look into.

Or Cdim/B!

Or B(b9)!

The root note would be wrong in the latter of those, Mario, plus I don't think BBox accepts a flat9 without a 7th of some sort.

EDIT: And the first suggestion, while a seemingly simple one, it's also not with the intended root (now that I had another look at it), sorry

Played in that inversion C-Eb-Gb-B on piano is a BMajb9

Which is why I made a point of specifying the intended root note as a vital part of the definition.
I am thus essentially asking what would you call this C chord... to which my own proposed CdimMaj7 (or the more obscure CmMaj7b5 suggestion) would fit the bill the most of the above. It's just that BBox has apparently never heard of it.

p.s. It's actually never heard of of some quite more straight forward ones either, I might add, such as Cm7b9 to pick just one off the top of my head...

Ya, this seems to be one of those times it becomes evident that BIAB is not the tool to use if you need to define voicing of a chord. So some midi workaround with freezing the track and then editing in the Piano roll would be needed.

There is a chord called Cdim(Maj7) so your proposed chord is real:

https://www.scales-chords.com/chord/piano/Cdim(maj7)

Eddie,

I used PG Music's +++ Piano Chord Dictionary +++ and obtained the results shown below. Based on those results the most likely name is B7b9. Note the Gb was changed to F# since the dictionary does not accept Gb in this instance.

I hope this is helpful.

Indeed, but obviously provided that one is going by midi in the first place! That particular issue becomes all the more pronounced when it's Realtracks

You know, that actually doesn't surprise me one bit, much like I'm quite confident in that the aforementioned Cm7b9 is equally real (and a hoist of others not found within BBox). They both are, as I said before, pretty straight forward, and one has to wonder sometimes about seemingly arbitrary exclusions like that within BBox's data.
Have thanks for that link reference, though, that's one for my bookmarks for sure

That reference only makes me wish they'd offer this thing for Mac!

Thanks for mentioning that Eddie.

I browsed through the Mac portal to find the link I provided thinking PG Music offered the program for Windows and for Mac. Evidently they don't and I didn't realize it until you posted your response.

Perhaps it's time for another wishlist request?

Ebm6#5

If you're going to try to use it in BIAB you'll have to use Ebm6

BIAB as Ebm#5 so combining this with Kajun Jeaux's answer above, it's worth trying Ebm#5/C.

Out of curiosity, what key is the music in at this point in the song?

I set it to Cm, although the intended scale is Locrian.
I have actually already completed and submitted the song, in case you're "curious" enough: https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=595731

I had planned to use that elusive chord for the ending only, but I ended up not using it at all, since it turns out that BBox cannot deal correctly with slash chords for the ending section in the first place (something I did not know until this li'l experiment, btw, and I've reported that as a glitch).

G#7(#9)/C ( root omitted )
Is how I would use this chord...