I could supply the island, but the bizarre thing is that I made a fresh “hello world” map using a weak mapped session-to-int variable, and it didn’t even work in the editor. I literally copied and pasted Epic’s example from the documentation.
I broke the process down into three steps and (a) writing to a weakly mapped session variable has no problem, (b) reading from that same variable in the same session, no problem (c) ending and restarting the game completely erases the previously stored variable.
On the other hand, my map created before the last two upgrades saves the round number(int) and shortest completion time (float) absolutely perfectly between rounds when run from the editor. You can play ten games in the same session, and it works every single time. Not in Fortnite.
This makes me think that projects created before the last two updates have the works-in-the-editor-not-in-the-game property, while projects created afterword never retain the global, session value in either in UEFN or in Fortnite. It’s like there is a storage spot for global variables in Islands created before the last two patches that no longer exists for newly created maps.
I posted this all in a bug report, my “hello world” map referred to in the report is the simplest possible map that displays the property, so it may save some time if someone is working on the issue. I can supply my old map if you want to look at something that works in the editor, it’s fairly involved though.
Bug Report
Private island with works-in-editor session variables: #8168-1632-6083