AsRock (and maybe other manufacturers) instead of using socketed BIOS chips has started using a specific BIOS_PH1 header.
Actually there are at least two different ones, both with 9 pin but with different size and pinout.
The more common one has two row 10 pin with one central missing.
Unfortunately on my B450M Pro4 the header is as follows (different shape and size):

I found this:
https://www.thelabeshop.com/files/5/3106..._Pin_Header.pdf
but it's still not clear how to connect the CH341A for programming...

you'd need to find out the model of the chip, then the package type from that. then you can buy a test clip for that package for the ch341a.

@elisw - Contact Asrock, and ask for pinout image, they should send you one since this is documented on the board. Looks like same header MSI uses forever, but that means nothing for the actual pinout.

Please share their reply if they give you pinout info, thanks. What are the two chips below SB heatsink, and one above? Maybe one of those three are BIOS, and the one near pinout you've shown is more meant for permanent backup?