All you gotta do is look at the bottom left of this boards index. In the display options section, there's a drop down tab that has 'prefix' on it. Click that and select 'Implemented'. It will then only show you threads that have the implemented tag.

Right now, 6 (lol) ideas have been implemented - https://i.gyazo.com/5f1b282ae0646605...42653f2ca6.png


So this can be fairly easily found already, but I'd agree that having a stickied thread listing them would be good for reference and accountability.