To add a separator before an extension point in the drawer, the UIX needs to manually call #drawerSeparator(), like the following example:
It has the drawback that if there is no item before the UIX, the displayed separator is useless.
We could have other problems like 2 uix defining manually a separator, but one of them do not display content because of an if, so at the end we have 2 separators in a row, etc...
A better solution, as implemented in
XWIKI-12636, is to introduce a separator parameter in the UIX and let the skin manage the separators (displaying it or not depending on the context).
It will also be consistent with