Grammarforge assemble now!

Isn't it an adverb in that context? The verb is "are"...

My mother the English teacher would be SO disappointed to find out that I don't remember all this as well as I should. But I am transitioning to a better focus on it.

To the extent "to effort" can be a valid verb, "are efforting" is a present progressive verb form, not an adverb. An adverb describes an action (e.g., slowly walking), an adjective (painfully loud), or another adverb (exceedingly nauseatingly telling the story).

Then it must be a new usage, or else a West-coast thing, because I have never heard it before and a quick look around internet did not show me that it was common, either.

I (like a lot of people) go by ear on these things.

But, as a stickler for grammar, I must concede that you're right.

"I've given presentations before X" or "I've spoken before X" are better alternatives to "I've presented to X."

However, if I were to get to vote, I'd choose to make intransitive "to present" an acceptable alternative to "to give presentations." It supplies a single verb in place of a verb and a noun. And it sounds good.