I tried typing Cdim---,Cdim7--- today
Then heard the same thing.
So, I understand that in BIAB, Cdim=Cdim7
Is it right?

Then, I wonder if BIAB has any authority to release which chords are.
thanks!

There is an interesting extensive thread on this subject. I’ll see if I can find it.

You are using RTs so you are at the mercy of the musician who played the chords. If the musician only played Cdim7 then you will get it on both Cdim and Cdim7. In another style another musician may have played both Cdim and Cdim7 so you will get that distinction. At least that is my understanding.

Based a number of your questions lately I think you should take some time and start learning music theory, at least where it pertains to chord structure. Most all of your questions would be answered IMHO.

thank you very much!
I'll keep trying!

In Options> Preferences. Double click on "Display". On the right there's a check box to treat C dim as a triad rather than a diminished 7th.