It would be great if there was a share extension for Scrivener so it would become a snap to through the share menu to be able to add a document being read in Preview, Safari and other relevant applications to a Scrivener project research folder.
I like that! 
Other than the need to “select” content, how is that different than the extension in services?
I think the software may already do what you are looking for. In the footer bar below the file viewing area (which may just be an icon depending on the type of research file it is) there is an application button you can click on to load the resource in another program, you can even choose which program, or what Scrivener should use as a default for that kind of file. For example you can load PDF into Preview, annotated it, save it and then when you refresh the view in Scrivener you should see the new annotations. You can also use the Ctrl-Cmd-O shortcut on a Mac, or Ctrl-F5 on Windows.
The service works for taking clippings from webpages or using a Print as PDF to Scrivener, but not for taking a PDF or image already open in Preview and just sending it to Scrivener. You can do something like this though by clicking and holding the file icon in Preview’s title bar, then dragging it into the Scrivener project’s binder to import it. I’ve found that a useful trick for quickly importing random things I have open.
Ah I see, the other way around, I was talking about loading things out of Scrivener into other software in my post. Yes, the title bar icon dragging trick is what I have always used if I have something open and want to put it somewhere else, or load it into another program. It basically just acts like a Finder drag.
I wonder how the “share” would determine which project, where in said project, and what metadata (not) to populate in the project. Seems like it would require scriv to be open to a project which … the drag method might accomplish.
Is an interesting thought exercise. Ioa/MM, how does KB evaluate these things?
Such a thing could in theory work similarly to Services or if you try to open a PDF in Scrivener. The software will target the “active” project, or the one that was left on the top of the stack when you tabbed out, and place the item in Research, or for Services that just add new items, there is a clippings folder. If there are no projects open, you just get a warning, and you will get the same warning if the program isn’t even running (it will launch, but the request to file the stuff will happen before any projects can open, assuming they automatically do).
But yes, I think drag and drop is going to generally be just as good as you get to choose where the stuff goes. Even on a small screen, there is usually space to leave a little bit of the Binder visible behind what you’re doing.
You can also drag between spaces/desktops, combine it with keyboard shortcuts like Cmd-Tab, or drag to the application icon in the dock, then to the correct project, etc. if your window is buried. I tend to find that using Services, my clipping don’t always go to the project I intended (my own problem from having too many projects open for too long a period), so I usually copy and paste or save a PDF somewhere I can then import it, rather than trying to go straight to the project. Most likely even with a share service, I’d still use the drag and drop method to make sure the item went where I wanted it.