You are correct in that I am asking about local to remote and remote to local transfers. After using WinSCP for several years I found I had lost several files because the default transfer had become MOVE rather than copy. I looked through all the "Options --Preferences" and didn't see anything I recognized as helpful. In desperation, I started checking boxes.
Whether it was this act of stupidity or something else, the default is again copy. BUT, I would like to know how this can be done/undone for future problems.
The default drag&drop operation between local and remote panels should always be Copy. No option should change it. If you ever face the problem again, please let us know.