Thanks, there was a new UEFI 2.50 for the ASRock AB350M Pro4. I reset to UEFI Defaults, and then flashed it using a USB drive.
(For some reason, previously, but only occasionally, there was a RealTek Networking item in the UEFI, that seems to have disappeared. Trying "Internet Flash" gave an error immediately, that there was no internet connection. Yet, in Windows 10, I have a wired gigabit connection to my LAN, which has a wired internet connection.)
Anyways, I tried setting the previous settings, which were 3800 Mhz core clock, 1.3250V, which I'm at now, but I also used to have my RAM overclocked slightly. I had my Team Dark 2x8GB DDR4-2400 running at 2667. I tried the same thing with the new 2.50 UEFI, and this time, the XMP timings are sticking, even though I chose a higher freq. for the RAM. Looks like I have to increase the timings manually. Before (with UEFI 2.40), it bumped them from 14-16-16-31, to 18-18-18-42 or something like that. (Verified with Ryzen Master.)
Still doesn't appear to have any UEFI settings for the LLC or SoC voltage, or offer an "offset" option for the voltages.