To start any of these, be in Boxes overview with the gray bar (with the "New" button) at the top.

This works as expected (for context):
 1. Click checkbox on toolbar to enter selection mode.
 2. Select a box.
 3. Click delete on the actions bar (which has appeared).

This looks broken:
 1. Ctrl-Click a box, choose "select all" from the selection menu, or right-click a box.
 2. The box is selected, but no action bar comes up.
 3. Select the box again, either by deselection+selection or choosing "select all" from the menu a second time.
 4. Click delete on the actions bar (which has appeared).

This is what should happen:
 1. Ctrl-Click a box, choose "select all" from the selection menu, or right-click a box.
 2. Click delete on the actions bar (which has appeared).

The bug appears to be that the actions bar only comes up when a box is checked and the UI is already in selection mode.