I thought this might be helpful for others...
You can remove all traces of your history by removing the following files:
C:\Users\[User Name]\AppData\Local\GPSoftware\Directory Opus\State Data\dupe.osd
C:\Users\[User Name]\AppData\Local\GPSoftware\Directory Opus\State Data\find.osd
C:\Users\[User Name]\AppData\Local\GPSoftware\Directory Opus\State Data\ftplast.osd
C:\Users\[User Name]\AppData\Local\GPSoftware\Directory Opus\State Data\lastrename.osd
C:\Users\[User Name]\AppData\Local\GPSoftware\Directory Opus\State Data\sync.osd
C:\Users\[User Name]\AppData\Local\GPSoftware\Directory Opus\State Data\MRU\*.*
To do that in a batch file, you can save the following code into a text file named dopus_clean_history.bat and then double click it. Make sure the path to Directory Opus matches your path.
@echo off
REM *** Close Directory Opus and DOpusRT.exe ***
"C:\Program Files\GPSoftware\Directory Opus\DOpusRT.exe" /CMD Close PROGRAM
"C:\Program Files\GPSoftware\Directory Opus\DOpusRT.exe" /dblclk=off
REM *** Pause for 3 seconds ***
ping 1.1.1.1 -n 1 -w 3000 > nul
REM *** Delete the history files ***
del /F /Q "%userprofile%\AppData\Local\GPSoftware\Directory Opus\State Data\dupe.osd"
del /F /Q "%userprofile%\AppData\Local\GPSoftware\Directory Opus\State Data\find.osd"
del /F /Q "%userprofile%\AppData\Local\GPSoftware\Directory Opus\State Data\ftplast.osd"
del /F /Q "%userprofile%\AppData\Local\GPSoftware\Directory Opus\State Data\lastrename.osd"
del /F /Q "%userprofile%\AppData\Local\GPSoftware\Directory Opus\State Data\sync.osd"
del /F /Q /S "%userprofile%\AppData\Local\GPSoftware\Directory Opus\State Data\MRU\*.*"
echo "Directory Opus history has been deleted."
I hope that Directory Opus can add a "Clear History" menu item or option in future versions.