Proton Mail detects duplicate image attachments but does not detect duplicate PDFs or other document types. When attaching 30-50 files, it's easy to accidentally add the same file multiple times with no warning. Additionally, the attachment tray at the bottom of the compose window is too small to effectively manage large numbers of attachments — making it difficult to identify and remove duplicates after the fact.

Requested improvements:

Extend duplicate detection to all file types (not just images)
Make the attachment tray resizable or scrollable for large attachment counts