After unchecking a search field, Logos 6.0b Beta 4 automatically resets Search Field drop down back to the Top:

Hence, trying to see if Tag, Title, Topic, ... fields have relevant results requires lots of scrolling.
Edit: work around is check new search field followed by unchecking old one before search completes. Puzzled by not being able to find Subject Index:

Surface Text field finds Subject Index in Contents, but Subject Index itself cannot be found, even when searching All Text.
Keep Smiling [:)]