thanks for your reply gazumped!
the gmail shortcut in question is:
`
Go to next inbox section
If you use an inbox style with tabs or sections, you can quickly navigate to the next section.
https://support.google.com/mail/answer/6594?hl=en
The 'tabs' I mentioned are (configurable like) 'Personal, Social, Promotions, Updates, Forums', and the defaults for clipper (in my region: AU, at least) seem to be ` backtick to 'Start Web Clipper'... I've confirmed this by clicking 'Reset Defaults'.
Just thought I'd mention since this is the result of