Calculation (rendered) symbols will have a Drawing symbol associated with them, but there are some Drawing symbols that exist separately and are not associated with any Calculation symbol. Symbols that only have a Drawing version can only be accessed when the "Different Drawing Symbol" option is selected. Selecting the "Different Drawing Symbol" option will also cause a blue rectangle to appear around the Drawing Symbols area, bringing focus to the fact that it is the Drawing symbol being changed and it is (or will be) different than the Calculation symbol.
If this is done, BOTH the Calculation AND Drawing symbols will appear in the list on the left side of the dialog. If one wishes to see ONLY the Drawing symbols, the "Drawing Symbols Only" box needs to be checked (see image below). Note, too, that the "Category" option needs to be set to "<All>" for Drawing-only versions of symbols to appear unless custom Drawing-only versions of symbols have been created in which case they would appear if the "Custom" or "<All>" Category is selected.