On the DM-620, can I rewind a file to a particular point so that I can insert, append or dictate over something I have just recorded?

No.  Unfortunately the rewind buttons will not work while recording a file using the DM-620. When you stop a file using a recorder in the DM series, it will immediately start a new file.  There is not an option to insert, append or record over data recorded.  Note:  You can pause a file and then continue recording Source: …

Is there a wireless remote available to control the Olympus DM-620 digital voice recorder?

Yes, the Olympus DM-620 can be controlled wirelessly using the Olympus RS-30W wireless remote control.  Although, originally designed to control the Olympus LS PCM Recorders, our testing has found the RS-30W to be a great add-on to the Olympus DM-620 digital voice recorder. IMPORTANT: If the suggested resolution above did not resolve your issue, please contact…