Currently:

It would be cool if we could just start tiling themes like the theme page as space allows:

When dragging the resizer/grabber to the far left so as to collapse the sidebar entirely, the mouse (and touch I presume) loses hold of the grabber requiring he user to re-click on it to drag it back out. The same behavior happens when dragging the grabber all the way to the right. It would be ideal of the “holding” state would never get dropped. If dragging to the left and it snaps to the far left edge of the screen, it could immediately bounce back to the minimum pane width if the user starts dragging to the right again.

Hey,

I am not sure what I did wrong but I cannot resize the customizer on my test site.

I am running WP 4.4-RC1-35761 on PHP 7 using Twenty Sixteen.

Checking the console I only have a warning "RESIZER-JS" but no JS errors.

The HTML <div class="customizer-resizer"></div> does get added to the markup so something is working.

We should consider adding a max-width on the favicon image (and probably the buttons underneath it) so it doesn't distort too much.

If I drag the resizer to make the pane twice as big, and then I reload the Customizer, the pane width should restore to the previously-selected width. It could store the user's pane width preference in localStorage.

The image looks fuzzy on a retina screen:

We should consider replacing the resizer image with an svg bar or a css shape.