Most pages import jQuery, which means we can then use jQuery in extension code.
The reports-view does not load jQuery by default. Therefore, we get this error in the JS console:
Uncaught ReferenceError: $ is not defined
at reports-view?FileID=RXRoaWNhbCBXZWIgRGVzaWduIChMZWlnZXJHYW1pbmcp:1:34472
Request: Can you please also import jQuery on the reports-view page? 
That way it is available to extension developers.
EDIT: Found some more views that don’t load jQuery. Here’s a comprehensive list:
- reports-view
- billable-expenses
- attachments
- emails
And some of the settings sub-pages are also missing jQuery: (not a comprehensive list)
- business-logo-form
- cash-flow-statement-groups
- chart-of-accounts
- control-accounts
- custom-fields
- etc