I like altering the mission files (ex. “BritishFighter1917.txt”) to add, or occasionally remove, mission types from the mix. I cut & paste from Bletchley, Bucksnort, and OldHat’s work, hardly being clever enough to do a original creation. Bletchley’s DOP’s are definitely something I add to the mix for the British.

Question: Everyone’s (including OBD’s) have a different number of total missions in the files. Let’s say the one I’m using has 20 possible entires. How is the exact mission being chosen? Is it a random selection from the ones listed?

Depends on what you select from the workshop settings.

Leave 'Historical Mission Types" in OFF position to get the best selection from 3rd party mission files. Turn it ON if using the default WOFF PE "Order Of Battle". That is my advise.

Really? Oops. I think.
Yet the third party missions still show with “Historical” checked or am I misunderstanding?

Correct. However, when turning it on, the historical mission setting is optimized for WOFF default missions. The 3rd party mission files already contain accurate proportions and mix of different mission types. So, it is better to not disturb that balance and allow random selection. That is what the MOD authors had suggested a while ago

Ahh. I wasn’t aware of that caveat.
Excellent. Thank you sir.