I don't seem to be able to add existing media from within my Media Library to a View.
Instead I have to upload the file directly from within Views itself. This is leaving me with a large quantity of duplicated files in my Media Library, which is something I would like to avoid if possible.
Is this expected behaviour?
That's correct, this is expected.
Views, Content Templates and WordPress Archives can only export images attached to themselves, hence we limit what appears on the Media dialogue to elements attached to the current object being edited.
Note, if you try this with Content Templates then you will see that you actually can see ALL Media.
That is a BUG, and it's not expected since you will not be able to export those in the CT export. This will be fixed in future.
To use Media in Views, CT or WPA you need to upload the media directly to it.
I also suggested to rename that button from "Media" to "Toolset Media" as it has nothing to do with what we expect on "media" from WordPress.
Thank you for clarifying this Beda.
Is there any reason for this configuration? Is it something to do with permissions or security?
I think your idea reference the rename would be useful and help to stop some of the confusion as to why all media does not appear there in the first place.
I have checked it in our to-do list, it is designed to "limit what appears on the Media dialog to elements attached to the current object being edited", for example:
If you export a view to another website, those images attached to that view will be exported too.
So there isn't anything to do with permissions or security.
Thank you for the information Luo Yang.
I gather there are no plans to change this in any way?
Yes, you are right, there isn't plan to change it in view, but it will be changed in Views content template.
Thank you to both Luo Yang and Beda for your help with this.