David,
Loyd has the right solution for you. The drop-down 'Symbol' list is comprised of the symbols from the saved .xdv and .dat files in the 'X_Dev\Data' folder. If you delete the .xdv and .dat files in the 'Data' folder it will remove the symbols from the list. However, you will also lose your saved files and settings.
What I have done is to make a copy of the 'Data' folder and save it somewhere else outside of the 'X_Dev' folder. In my case, C:\Program Files\XdevData. I open and save .xdv files there.
However, each time you call for a symbol in the program, it will still automatically create a .dat file in the 'X_Dev\Data' folder. Consequently, the symbol will be back in the drop down list. You will still have to go back in the 'Data' folder and delete .dat files to keep the 'Symbol' list empty.
Is that clear as mud?
Of course, please do this only if you are comfortable working with folders and files this way. I wouldn't want anyone to be deleting or changing anything in the X_Dev setup that would cause program operating problems.
Note to Myst and Yong for future releases: I do find the 'Symbol' list of minimal value. The reason is that if you select one of the symbols, it uses whatever settings are already being used by the program. It would be more useful if by selecting a symbol it would actually open up the .xdv file itself with its own saved settings. Just a minor.
Happy Labor Day Weekend All!
Steve