This folder contains certain settings used by VBox. For example, it stores whether or not you have decided to not be informed of the mouse capture feature when enabling it, upon other things. This folder thus may be remove if you so desire, though note that this will delete certain settings and, that VBox shall create the folder again, once you decide to use if afterwards.
Thank you very much for your detailed answer. This helps me to understand the utility of the folder. Deleting it wouldn’t have sense if VBox creates it again…