is there a Thunderbird add-on that would find and parse mails like the following and give the user the ability to quickly add the given time and date to the calendar?
Dear Foo,
I suggest we meet _tomorrow at 10am_.
The idea here would be to transform tomorrow at 10am to a clickable link that would result in the creation of a new event in the calendar.
This is more of a superuser.com question the way you are phrasing it. The built in way to do it is to use the context menu, then convert to, then event or task. It may not catch all kinds of dates, so "tomorrow at 10am" may not work.
There is also a toolbar button you can add from the customize menu that does the same thing but allows you to select the language to use for detection. Make sure you are using a multi-locale Lightning for that (e.g. one from addons.mozilla.org).
I've always been wanting to write an extension that allows you to select event details manually, but I never got around to finishing it.