Add subscription to existing calendar

I'll be honest, this feels like an "I'm just overlooking a checkbox" kind of a problem, but so far Google hasn't found a solution for me.

There's a meeting series hosted by a public entity which publishes their calendar as an outlook subscription so you can get a copy of it and keep it up to date. However, when I go to add it to outlook, the only option is to add the subscription as its own standalone calendar. This is pretty much useless to me as the second calendar that it adds doesn't block my main calendar, sound meeting reminders, or any or even show up unless its specifically turned on.

Instead, I want to subscribe to the calendar and have the events on it added to my main calendar, just as if I had imported the events from and ics file. Any suggestions for how to do that?