Mail no longer suggests mailbox to move to on Mac, and IOS
“You're not able to force Mail to forget your previous "Move To..." choices. Mail will update them automatically, with repeated usage and the passage of time.”
In researching the vanished capability for Mail to suggest a mailbox to move to, I came across the above partial answer. No where else did I find a solution to my problem. It worked well for years but I now have to select the recipient mailbox my self! Hopefully there is a simple explanation!
iPad mini, iOS 9