That's what it looks like the $49.50 "Adding Benefits" fee do for you. A friend of mine just paid that after her outbound hoping to be able to then upgrade the return. Her fare class changed from Basic Economy (N) to T (shown on the invoice as: "Switch Basic Fare To United Economy") which should have allowed her to make changes. WineCountry posted the benefits of paying the "Adding Benefits" fee from this link https://www.united.com/en/us/fly/tra...c-economy.html in the post before yours.

My friend didn't see the fee option on the app, but did see it on .com when looking at the reservation.

As for the upgrade issue I had posted a question about, unfortunately I do not have an update. PZ never opened up, so I didn't call. My friend was too preoccupied with family stuff to spend time on a call to United, so I do not know if there was a glitch or if upgrading by instruments/cash upgrade is not supported for converted BE tickets. I suggested she call United after getting home about not being able to "upgrade" to see what the deal was and potentially get her fee refunded.

In the end, I think my friend would have benefited from two one way tickets. She didn't care about BE restrictions on the outbound, but the return was a redeye, so she wanted to try and get a decent seat for sleep. Maybe she should try BE outbound, economy return to save some $$$ but keep flexibility where desired.