"Read More" Break

I'd like to request that a "Read More" button be added to the Advanced Editor.  We need the ability to choose our own summary text block for the blogs index.  Sometimes I like a single paragraph, sometimes two or three, depending on the content.

The "Read More" button would put a placeable dotted line in my blog body to indicate that text above the fold goes into the summary/index page, and anything below the line is only shown on the full blog page.

Thanks!