Add new setting for garrison instant WQ and for Blingtron to show when not completed. It would display a red X (and when completed it will change into the green V). The utility of knowing this (and the easier way to notice when not completed, at a glance) would be higher than knowing that you've completed these, after the fact, if you ask me.

Ok. So another setting that acts like the world bosses setting then, correct?

Well, in a way yes, could be said it's something like the world boss setting. Just that this would complete something on the corresponding line too. For Blingtron it could be a plain tbing without any check, like (when the setting is enabled) just display the red cross until it receives the flag that quest was completed. For garrison instant WQ maybe some caching involved? It woud basically reset towards X red cross when the V checkmark expires, but only for those chars that already had the instant WQ.