Excellent feature, and it's one that I looked around for, before I found I had to create Document items to store files.
1) "file name" label, and thoughts on describing files:
There's some value to describing the nature of a file, in case the file name itself isn't sufficient. (Certainly when adding a photo from camera roll on iOS, you can't create a meaningful file name, but are stuck with IMG_ or something equally meaningless, unless the file was imported to the Photos app on a Mac and then synced to the camera roll, in which case it retains the original file name.)
In Document items you can, after all, just name or rename the Document item to whatever you like to describe the file. And you can now similarly create any other Item type, name it descriptively, and put one file in it. But if you didn't want, say, multiple Medical Records, but wanted just one with multiple attached files, naming the Item itself wouldn't be an adequate solution.
When creating or editing a File field in an Item, there's a label called "file name", which you can modify while editing, but I discovered the label text isn't visible when saving the Item, and it reverts to "file name" when editing again. I guess it serves more like a prompt while editing than a label, and I see that in general labels are a bit inconsistently implemented across 1Password - sometimes they can modified, sometimes not, though either way the labels still seem to appear when viewing Items. (For instance, you can't modify a Login's "username" or "password" label, or the "notes" labels, but those labels do always appear when viewing the item.)
Maybe the simple solution is to not allow the "file name" label to be modified and not worry much about the whether that label name appears when viewing the Item - it's redundant to the "View Document" or "Quick Look" text.
The best way I found so far to add a description of a file is by placing it in a named Section. I found I could accomplish this by adding a field of type "File" in some section. But inconsistently, when using the "Add New File" button, files wind up in no Section, and a section name can't be created for them - you just have some free-floating files that you could only describe in the "notes" field or other text field.
2) The "Add New File" button:
That button highlights that the app has a cool new feature, but is inconsistent, since you can't create other fields through a dedicated button. So it seems to muddle the UI, though the new feature would otherwise not be obvious. I can imagine there might have been a debate about including that button, and I don't really have a suggestion.
1Password Version: 7.8.8
Extension Version: Not Provided
OS Version: Mac Big Sur 11.5.2