So the personal variations are stored as a sequence of moves embedded in a private chat message, the game tree is not persisted, but that branch will be recreated when you click the variation msg. Notes exist in the chat stream by timestamp, not on move nodes in the game tree. This means it is useful for recording a few variations (and being stored on OGS rather than locally is handy for playing from phone then desktop), but not in-depth analysis of dozens of branches with comments on the nodes for e.g. endgame calculations. But I expect I was unusual in doing that deep a level of analysis.
Anyway: Kifubara: Go board scanner — take a photo of your board, get the score + SGF 