Symbol Extensions
when attempting to adjust symbol extensions you may not see any groups displayed. this is because the extension group is defaulted to none.
in order to activate extension groups, click on the drop arrow next to the wheel, mouse over restore defaults and choose which extension group you would like by left clicking on that group. 
please note that with this setting, to enter dually listed us based symbols you will need to add a dashus extension to the symbol. example: abc-us or t-us