It appears as though the file-sessions.json file is hard-coded to be in the App_Data folder.
Right now, in the current version of GroupDocs.Annotation for .NET and all others file “file-sessions.json” is hard-coded to be in the “App_Data” folder. There is no way to change its location.
But we reviewed your proposal and we are agreed that it’s causing annoying problems when using source control systems. So we have decided to implement an ability to change location of “file-sessions.json”. It already is present in our roadmap. New version of the Annotation for .NET that contains this feature is planned to be released on the next week.
If you will have more questions please feel free to contact us.