How can I setup DELETE settings that have expected results

I am pulling my hair out these days trying to understand DELETE and all it’s options. Cut to the chase:

I just want e-mail I delete on K-9 to end up in some folder back at the server that is not INBOX
so that I can decide how to deal with it further and not lose it until I decide to do that.

there’s one fly in the ointment the server I use with SQUIRREL mail has a “DELETE BYPASS TRASH”
option and I’m wondering if that’s interfering or is that a red herring of mine?

For me it sounds more like MOVE than delete.

Deleting a message in K-9 Mail will move the message to the configured trash folder. Only if no trash folder is configured, the message is deleted immediately.

You can configure the trash folder under Settings → [Account] → Folders → Trash folder.