So as the title says I’ve returned after a long hiatus from ED. I know the galaxy map used to show systems I had visited as blue but it no longer seems to do so. Is this permanent? Or is there a filter I am missing or have turned on that is blocking this function? I like to clear/explore large sections when in the black so knowing where I’ve been by looking at the galaxy maps saves a huge amount of time.
Oh boy, you might be in for a disappointment. This filter still exists, please see above.
BUT.
This filter depends on a file locally saved on your computer. As far as I know, it's the only information shown on the in-game galaxy map that doesn't fetch its data from the servers. So, if you deleted the game and have just re-installed it now, this file is probably gone for good. The file is called
VisitedStarsCache.Dat
and is located in
%LOCALAPPDATA%\Frontier Developments\Elite Dangerous\[cmdr_id]\
If you have visited 2500 star systems or more, it should be bigger than 25 KB. If your current file is just 1 KB or so, then I'm afraid all is gone. However, if you have been using an EDSM account, you can use the EDSM export function to recreate the file.
I wrote a short How-to here.