It has worked. Here’s where I stumbled:
1- inputting the mnemonic for my sapling addresses and generated by
zcash-cli exportwallet (zcashd 6.2)
into YWallet 1.8.1 did not work. YWallet did not explicity inform of the failure, however, as Auto had clearly stated that it wouldn’t work, I didn’t waste alot of time trying to get it to work.
2- Further following Auto’s instructions, I created an account for each sapling address I wanted to import to YWallet 1.8.1. During the import, I was sure to paste the privkey INCLUDING the “secret-extended” prefix into YWallet. Then, I started a rescan in YWallet and it’s beautiful progress bar appeared across the top, 0% on the left to 100% on the right.
Incidentally, I could see the rescan progress bar intermittently flickering as I tried in vain to use the mnemonic in my attempt (1) above…forget it. YWallet wants to do it, but it can’t! If you don’t see the progress bar moving from left to right over a couple of hours and instead see it flickering off and on…it’s a fail.
I hope this helps someone else, thanks again Auto and dismad.