When using "Combine files" functionality, the order in which the document thumbnails appear used to (logically) depend on the order in which you selected the files. The document you want first in the combined PDF, you selected first, and then other files in order. Now (the last 5 years or so) no matter what order you select the files, they are always in...alphabetical order (?) in the Combine Files window. Why lose this great functionality?