I don' t normally upload two items on the same day, so I haven't come across this before.

During uploading, I tend to save the upload about twice and was of the opinion that after I have either selected the Bye Pass Queue or the Moderator's Queue, that the "saves"(if any) would be removed.
As you see from the pic, that doesn't seem to be the case:


Is it the following day that any "saves" are removed?
Does that mean I could edit the uploads from the "Upload Items" location or would that trigger issues?

Saves are never removed automatically, I'm not sure where you got that piece of information. You have to remove saves yourself manually from that list.

Editing the upload after submission is a totally different process and nothing to do with the upload wizard.

Hope this helps

Thank you for your prompt reply.
So when do the saves disappear?
I assure you (with an odd exception of eliminating a previous save if I have edited the upload) I have never removed all the saves myself.
My apologies to the person who might be doing this for me - when exactly should it be done i.e. after submission of the upload?

You can remove them whenever you want, usually after a successful approval.