Can't drag directly from Active Toolbar to Available Buttons 2nd row

In Drupal 8.0.0-beta1, given a two-row arrangement of Available Buttons:

To move something out of the active toolbar, it is not enough to drag the button into the two-row rectangle of available buttons. You have to move it before the last available button. Moving an unwanted button, e.g., strikeout, immediately to the right of the Styles button resulted, unexpectedly for me, in no change. I also tried dragging it into the second row of buttons to no avail.

Steps:
1. Go to /admin/config/content/formats/manage/full_html
2. Adjust browser window size and/or zoom of browser such that Available buttons spans two rows
3. Drag the subscript button (x-sub-2) to the 2nd row of Available buttons.

Actual result: Highlighted position remains in Active toolbar
Expected result: Highlighted empty position appears in the Available buttons array, ready to receive the subscript button. No highlighted position in Active toolbar.

Workaround: Drag into the first row of Available buttons. If you still want it to be in the second row, you can now drag it back to that row before releasing the mouse button.