Easel's image editor, invoked by selecting Open in Editor from the image menu, allows you to perform all standard editing tasks while working with a larger copy of an image than is possible when working on the image directly in Easel.
When an image is open in the editor, you can invoke the image menu from either the main editor menu bar or by right-clicking on the image. The editor image menu has an additional entry, Image Size, that lets you work on either a scaled or full size copy of the image.
When you are done in the editor, select the appropriate entry on the file menu: File/Save changes & return to Easel or File/Discard changes & return to Easel.
Note: There's a reason why Easel's image editor is nothing special. I was working on a much more capable one when Google started giving away Picassa, which includes a very nice editor. I didn't see much point in continuing. The editor does what it needs to, but if you want more, go get it for free at www.picassa.com