In expressions or articulations, if one wants to delete all elements (before loading a new library), it is an easy operation : shift/select the first and the last element, then click on the Delete button.
In the Staff Styles window, styles can only be deleted one by one !
When I want to replace the current library by another one, I sometimes have to delete 50 staff styles one by one, which is time-consuming.
Suggestion : a "Delete All' button.
Thank you for your attention.
P.S. : sorting the staff styles is also inconvenient. The solution is to number each style. But if I want to modify their order or insert a new one, I have renumber them one by one.