The badge on your nation for answering an Easter egg issue(s) answered does show the number of Easter eggs (in the alt/hover text), but there's no way, as far as I know, to tell which specific issues. When nations are hunting for Easter eggs, it would be helpful to know which ones you've already found, especially if the nation has been around awhile. From a technical side, it seems like records of this are kept (example), but asking the mods for those records is not a sustainable method.
My suggestion: a page where it lists the issue titles of the Easter eggs your nation has found (or the effect line of the issue choice chosen). To preserve the fun and semi-secrecy of Easter eggs, the page could only by viewed by the logged-in nation themselves; you couldn't see other nation's Easter egg lists. The page might be accessed by clicking on the Easter egg badge on your own nation (making the page itself kind of an Easter egg if it's not linked anywhere else!).