OK, so this does work, albeit a royal PITA.

First, if anyone is wondering I needed to use an eTicket for the Amex Companion Certificate that I had previously cancelled. Unbeknownst to me, Delta now seems to issue eTicket instead of eCredits in this case. And unbeknownst to me, you cannot use an eTicket with the Companion Certificate.

AND to further complicate, my eTicket that was issued was set to expire 1/26/25 and I needed to travel in Feb.

So:
1) "Convert" eTicket to eCredit by other poster's recommendation to purchase a "cheap" ticket and the system is supposed to convert the remainder eTicket to an eCredit. DL.dumb said it would do that, but it kept giving me an error. Called in. Even phone reps were getting the same error and couldn't figure out why. Took about 30 minutes and several escalations and they finally booked "cheap" ticket and I ended up with an eCredit.

2) However, eCredit still has 1/26/25 expiration date. Now i needed to extend it. So do the usual trick (book slightly more expensive ticket, wait 3 days, cancel it). This DOES extend the expiration date, BUT it also re-converted BACK to an eTicket. Ugh

3) So now I have to repeat #1. Again, cannot book ticket, have to call in, phone rep easily fixes whatever is mucked up in DL.Dumb system. Now I have an eCredit with new expiration date.

Then the sage continues (will probably post over in the Companion Cert) but basically the DL.dumb system will not let me use the eCredit. Nor will it let me use the $100 eCredit that DL gave out due to the DL Reserve increase in AF. Called in. Phone rep said she was aware that you cannot use eCredit with Companion cert to book online (have to call in -so it's apparently "known bug"). But she also said the system wouldn't let her use the $100 eCredit the DL issued either. So I'll have to book a separate trip for that one.