Currently, if you want to clear browsing data in Firefox Android, you get a single option to clear "Browsing history and site data". As far as I can tell, site data includes websites' local storage.
It would be great to be able to select those options separately, since they are very different. You'd want to clear cookies and site data to make websites forget you. Browsing history is not accessible to websites, so you'd want to clear it only if you wanted to "forget" the websites you visited.
If it needs to be combined with something else, it'd make much more sense as "Cookies and site data".