The question you have relates to Post 3068, which suggested something along the line of (a) have only the hotel room cost on the folio and then crediting the stay (folio costs) to Marriott for EQN/Bonvoy qualification purposes, and (b) having all other on-site incidental expenses not charged to the room (e.g., paying for them separately in cash, or charging each transaction to a credit card at the time of purchase) and providing Identity membership information at the time of each purchase so that those purchases would be credited to the Identity program.

I agree with the parenthetical in the post which said "that sounds like a pain".

Edited to add:

From the Identity FAQs on how to earn spend: "Show your Identity card at the time of transaction, charge to your room, or present a paid receipt to the Identity Desk." Highest pain point for me would be to show your Identity card at the time of the transaction. Presenting a paid receipt to the Identity Desk is less painful in my opinion.

And if you paid for each separate transaction with a Marriott-connected credit card, you wouldn't lose out on the credit card points (assuming each charge comes through as Cosmopolitan of Las Vegas on the cc statement). Note: I've had difficulty getting Bonvoy points from Chase for paying with a credit card on restaurant meals at an Autograph Collection hotel restaurant that wasn't part of a stay. Hoops were jumped through, but they eventually posted.