Well, well: in My Home, there is a Maintenance section, and one of its subcategories is Cookies. With fear and trepidation, I clicked on it, and was presented with a big chart, nothing of which made the slightest sense to me except for my name and the word Password. Below that, however, there was this:
Expiring (deleting) your board's cookies might be useful if you suspect that they are damaged and the board is malfunctioning.

Expiring these cookies will do NO harm at all but it will log you out of the board. Once you login and start using the board again new cookies will be set automatically.
HTH.