Storing bookmarks fails on local machine

I have a problem with Spark 2.6.3 on Windows 7 Enterprise 64bit.

Bookmarked conference rooms are not remembered between Spark sessions. After closing down Spark and restarting, any bookmarked items are missing / invisible.

Enabling ‘Enable Private Data Storage’ in ‘OpenFire: Server --> Server Settings --> Private Data Storage’ stores the bookmarks on the server and this does the job, but I would like to store the conference room bookmarks and autojoin settings on the local machine.

From the description of the Private Data Storage setting in OpenFire I conclude that it should be possible to store it locally.

Any suggestions?