Library import asks for a location to file the cards under

After picking a file, Import cards… asks where the cards are kept,
pre-filled with the file's name (a ManaBox export is named after its
binder). A location is set on every imported card, replacing any it had,
as Add Cards does; blank leaves locations alone. It's applied inside the
import's single transaction.

README.md

@@ -237,7 +237,10 @@ match any printing still imports the card itself.
 or binder, either the `.txt` or the `.csv`. Both add to what you already own.
 The CSV names each copy's exact printing and finish, so it's the better of
 the two. Condition, language, prices and the other ManaBox fields aren't
-kept. Proxies count as owned copies.
+kept. Proxies count as owned copies. After you pick the file, the import asks
+for a location to file the cards under, pre-filled with the file's name (a
+ManaBox export is named after its binder). Leave it blank to keep cards'
+current locations.
 
 > The picker's dates and languages need card data from this version. Until you
 > update it, printings are listed without them. Whenever your card data is