This something that is built-into Chrome, so the Chrome online documentation is the place to look. (Do not expect Trimble document this, as it should already be documented.)
I just updated SU. I can now use the dev tools. Awesome.
I just tested one such Web app I have. The debugger can’t be opened even with shortcut keys.
If you open the dev tools first (by loading google for example), then change the url back to the ‘locked’ web app, you can debug. The dev tools are opened in a separate window but remain linked to the HtmlDialog they were opened from.