Can't update attachment fields

I’m building a “help” panel for a custom post type. Its going to use images marked for use in this panel. The way I’m doing that is using the attachment_fields_to_edit and attachment_fields_to_save hooks to add a checkbox.

But now, when I want to simply edit existing images uploaded to that post, there is no way to do it. The only option is to “Insert into post”. I can see the checkbox, but what I want to do is check it and click “Save changes” or “Update”.

Even if I select an image click “Edit” , then there is no option to save changes, and this seems wrong from a user interface point of view – “Insert into post” is not an appropriate action to exit an edit screen.

Actual behaviour:

1. Click “Add Media”
2. Click “Media Library”
3. Select “Uploaded to this post” from dropdown filter
4. Select an image (previously uploaded)
5. Attachment details appear on right with custom checkbox “Use as help image” visible
6. No option to check this box and save changes – only “Insert into post” which I don’t want to do

Expected behaviour would be as above but with the ability to make changes to attachment meta and save them WITHOUT inserting into post.