This is made from pictures. It's not real.
I don't know if it's complicated for the BIAB team to make keyboards for chord builders?
If it's not complicated, just add a keyboard.

SwingBabyMix,

That is a very nice looking mock up. If you make the suggestion to add a keyboard to the ChordBuilder window I will gladly support the idea.

Thank you. Everyone believes that BIAB will continue to improve

You might get some ideas from this:
ReaChord - My Chord Track Solution

I already asked this in the Reaper forum but I could not get an answer:

This sounds useful, I tried to install and run it, but without success.
I tried to follow all instructions. I already have the 4 scripts installed. I can create the 2 auxiliary tracks (Script: ReaChord_Act_Item2Sound.lua), I can start an open the chord view (empty, no chords) by running ReaChord_Reader_Start.lua and ReaChord_Reader.lua

But at any moment, when I hit ReaChord_Main.lua I get an error message that I cannot debug:"ReaChord_Main.lua:23: attempt to call a nil value (field 'ImGui_ConfigFlags_DockingEnable')"

Do you think I need to install something else apart from the 4 scripts for this to work?

Thanks

Do you know how to make it work?

https://forum.cockos.com/showthread.php?t=250419

And in ReaPack
ReaImGui: ReaScript binding for Dear ImGui

It was this. Now ReaChord works without any problem for me, it looks simple and powerful. Thanks!

Is this a VST?

It's just a Reaper script.