UI doesn't match behaviour described in documentation for MB Views. When following the documentation for MB Views here, the UI doesn't behave as described.
Group fields are marked with an arrow on the left, just like the image above. Clicking on the arrow will toggle the group sub-fields.
Clicking the arrow doesn't toggle the sub-fields in the list.
Clicking the label doesn't toggle the sub-fields either, and inserts the text INSERT SUB-FIELDS HERE
into the editor.
I have tried in Safari 13.1, Firefox 76.0.1, and Chrome 81.0.4044.138 on macOS X 10.15.4 Catalina; WordPress 5.4.1, Meta Box up-to-date with latest.