So it turns out this doesn't quite work. It shows the modifiers, but doesn't include the Proficiency modifier when displaying the final roll.

My current workaround is to add brackets around the parenthesis that give the names of the abilities. It works, but it does end up with some extra brackets in the display.

?{Select Ability|Strength, [[@{selected|strength_mod}]] [(Strength)]|Dexterity, [[@{selected|dexterity_mod}]] [(Dexterity)]|Constitution, [[@{selected|constitution_mod}]] [(Constitution)]|Intelligence, [[@{selected|intelligence_mod}]] [(Intelligence)]|Wisdom, [[@{selected|wisdom_mod}]] [(Wisdom)]|Charisma, [[@{selected|charisma_mod}]] [(Charisma)]}@{selected|pbd_safe}