You can check Quest completion InGame with an easy "/quest" command. You can do this individually or by creating a macro like the below.

Macro example:

/quest 58634

/quest 57373

/quest 57374

/quest 58615

/quest 58631

/quest 58632

How to use the addon:

1. Find your Quest ID on the battle.net or any online database like wowhead, thottbot etc. (quest ID is in the link e.g.: wowhead.com/quest=44581/spicing-things-up)

2. use the slash command in-game /quest 44581 (or create a macro if you want to check more than one quest at once)

3. You will get a return message like: <Tyllus'QuestComplete> You already Completed [Quest title] OR <Tyllus'QuestComplete> You did not complete [Quest title]