When I right click on a pending invoice, I don't see an option to delete it in the context menu:

So how do I delete a pending invoice?
When I right click on a pending invoice, I don't see an option to delete it in the context menu:

So how do I delete a pending invoice?
You need to open the invoice by double clicking it, and then in the dialog itself there is a delete button:

Click that button to delete the pending invoice.