Hey @William,
Unfortunately, getting around that “In-this-month” search filter would take some extensive modification of core plugin code 🙁 We don’t officially offer any support which such customizations, but even if we did, this would be highly recommended against because it’s a pretty tightly wound system that keeps the searches in the proper place.
If you’re curious about what would be involved, the simplest method I could think of would be to head into your plugin files for The Events Calendar and locate this file: src/Tribe/Template/Month.php
This is the specific code responsible for handling and limiting those searches: https://gist.github.com/ggwicz/9192ceffc8810e823072
So, if you’d like, you can use that code as a jumping-off point and work backwards from there to loosen the monthly limitation on search. That’s something we’d unfortunately not be able to help with, but I wanted to at least share something here 🙂
Sorry to disappoint @William! Let me know if you have any thoughts on this or if I can help with anything else.
Cheers,
George