First, for all the styles that you want element templates for, take a copy of your XIN file and make sure that the styles has a surface configuration and toggle on that you want the components displayed and once done, save the changes to the copied xin file.
The following needs to be done in SS3: Now while in style manager, toggle the filter for listing the styles that Include Surface. Select all the styles you want their symbologies to be created as Element Templates. Right click in the list of styles and you should see Export to XML.
Now select Element > Element Templates. File > Import>From XML file. Select the xml file you just created and have only the Element Templates selected. Select OK and in the dgn (or dgnlib) you had open, the Elements Templates are listed.