The command is in xfce4-terminal, but it is not in konsole. I would like that it was added to konsole.
https://helpmanual.io/builtin/readarray/

And if possible other missing commands.
https://helpmanual.io/builtin/

UPD: Not observed that there is a special topic for konsole.

You can't add bash built-ins to konsole.

The order is:

Bash -- Konsole -- Graphical Interface

Konsole sends you input to Bash. At the end you see the answer of Bash on your screen.

You're right. The topic is closed.