Something like this?
You can use Text in chart on Presentation tab:
Once you are on add window you can change the font to make it look bigger
The text might appear on the side, but you can bring it to the middle by pressing Ctrl + Shift and then moving the text within chart object to the middle.
I hope this will help. Attaching the qvw for your reference.
Community_174948.qvw 147.8 K