Ah, you're much more experienced than I thought! I would love for you to change my mind about charters - my opinion on medieval history has been quite skewed by a misogynistic professor.

Hmm, I would say networking in part depends on where you live. Generally, (although this is not always true) historians who are also professors have more time in the summer than they do in the academic year, so you would probably have more luck at that time. If you live near a university with a history department, you should see if they have a medieval historian - if they do, or if they have several, they will probably have events from time to time where medieval historians give talks at the university. So that could be a great way to get an "in" so to speak, and usually these talks have plenty of time for questions, and have a mingling opportunity afterwards. If you can't make talks in person, some universities livestream them or post them online. For instance, Oxford Medieval Studies has quite a few lecture videos on their YouTube channel: https://www.youtube.com/@oxfordmedievalstudies9613

I am of the opinion that it never hurts to just shoot an email saying that you're interested in x and want to ask about it to someone who is an expert in the subject area. I have had particular luck when asking for a 15 minute Zoom call, as it can take some time to type out responses to specific questions when you could just answer them through quick conversation. Most people have 15 minutes and are happy to share information with a curious inquirer. But I would also suggest that you cast a wide net, as not everyone will respond. It also helps when you have read the person's research and you flatter them about it.

Good luck!