In PassFailGraph widget:
Instead of "Show only failed" and "Show only critical" checkboxes, I would suggest having 3 check boxes as follows:
"Show Success" "Show Failed" and "Show Skipped/Critical".

Since Robot 4.0 Criticality has been removed and the checkbox for Critical test cases will only isolate skipped (failed-noncritical) test cases.

It's more useful to have a view where one would have  a combination of both "failed critical" and "failed noncritical".

With the aforementioned combination of check boxes it is possible to achieve this and maintain a level of compatibility with older robot framework versions, and it gives users a more finer-grain control over what is displayed in the widget.