Wants to edit the extensions listed in "List Files of Type" of Open dialogs.
It is not possible to edit the list. The following variables control the file extensions in the open dialogs.MS_DESIGNFILTER controls what file extension the open dialog windows look for, but is only active after selecting the DGN extension in List Files of Type drop down, it can be overridden with the *.* file extension.MS_OPENDESIGNFILEFILTER controls what file extension the open dialog windows look for all the time, but can be overridden when selecting a extension in the List Files of Type drop down.Any extension can be selected and opened, after opening that file, the files extension is added to the List Files of Type, and the addition is saved in the User Preference file (*.upf).