I want the iPad Pro to replace a computer so bad, but I just signed a PDF in Gmail, Gmail needed to save the file to Files, but can’t attach files *from* Files, so I had to download Google Drive and export the file from Files to Google Drive so Gmail can find it. 🤦♂️
While I fully understand that you are probably generally happy with gmail and don’t want to change, I use gmail from the iPadOS mail.app and have no problems with the exact scenario you describe. If you need to do it often, it’s worth a look!