Can anyone tell me if it is possible and how I can switch from ftp command line to local command line back and forth without re-establishing and disconnecting ftp connection each time?

two command windows?

If this is about DOS window command line with the ftp command, you can't, once the ftp command is started, IT has control and only quit will return control back to the DOS prompt.

Well, it's Linux, but the answer is probably the same