Thank you for your post.
If no fields are displaying the in Fields pane, then you may have a damaged Library.
Backup your current database file, and then revert from your last weekly backup. Do the fields show in the Fields pane? If not, then go to the previous backup.
If you have made a lot of changes since your last backup, export the data from your current library to text files, and then in the backup database file, import the text files so that the information is up-to-date.
Let me know if you need additional clarification.
I backed up my Bento and then checked for updates. There was one so I updated it and when I reopened the program the fields were in the fields pane as they should be and I was able to drag another media window into the record window.
I'm so glad it's fixed and wish Bento was still available but at least I can get help and the updates..... I wonder if I can get the last version?
Bento 4 is the last version, and it is no longer available for updating.
If you purchased through the app store I believe it stores your purchase and all the available updates until it was discontinued even though it is no longer available for purchase. I had Apple explain it to me once when I had trouble with Bento. Not sure if Bento 4 was ever a free update for another version.