I've been working on My Highlights again and I'm glad to share that I've added two new features: a filter on the import dialog and importing highlights to journal pages.
Filtering Books
After opening your clipping file, you can enter a filter to do a search by book title or author. It uses a fuzzy search library so you don't need to enter the exact phrase.
Journal Import
By default My Highlights will now import highlights and notes from your clippings file into the journal for the date the highlights were made.