I'm pretty sure I detected a small CSS bug regarding Extended Search: There is not enough room for the dropdown menus in the finder filters in desktop mode (s. SearchIndex_CSS_Issue.jpg).
I applied the following CSS in my custom.css file:
.finder-selects {
height: 330px;
}
After that the area looks like in SearchIndex_CSS_Issue_Corrected.jpg.
You might find a better solution, but I'm happy with my solution for the moment.
Regards
Rolf