I don't have the skills to create a new UI plugin, unfortunately.
Maybe I haven't been specific enough.
Currently ImageGallery uses rel="shadowbox[gallery]" to link the images when they pop up in to a set.
What would be useful is if you could choose and change the [gallery] part which links them.
So each thumbnail just has rel="shadowbox" and opens on its own. Then you could choose when you desire a set, these images would then become rel="shadowbox[set1]". However the images would not be visible as thumbnails only the first one.
<a href="photos/one.jpg" rel="lytebox[set1]" title="Blah blah blah! caption"><img src="photos/one.jpg" alt="photo1" width="145" height="100" border="0" class="image" id="photo1" title="Blah blah blah! hover title" /></a>
<a href="photos/two.jpg" rel="lytebox[set1]" title="Blah blah blah!"></a>
<a href="photos/three.jpg" rel="lytebox[set1]" title="Blah blah blah!"></a>
Also if you have two title="" it produces one for the hover title and a second for the caption.
Perhaps I should of posted this in the features. It's easy enough when hard coded. But would be very useful for the CMS. Hope that makes sense! Thanks