add edit button in squares

[mneuschaefer]

When I include an iframe embed to a square, it is only possible to edit this iframe when I click outside of its area. An "Edit"-Button (top right?) would make it much easier to edit existing content.

try with this iframe:
<iframe src="https://h5p.org/h5p/embed/362759" width="800" height="800" frameborder="0" allowfullscreen="allowfullscreen"></iframe><script src="https://h5p.org/sites/all/modules/h5p/library/js/h5p-resizer.js" charset="UTF-8"></script>

Editing would start when either double-clicking an existing square or clicking once on it (=buttons appear) and then clicking the edit button.

Example:

[mneuschaefer]

(see UI slides: https://docs.google.com/presentation/d/1NvHgqwmQuJguAoU0G2bbBaeWv8Zr5yRbvQd_LWUeYW4/edit#slide=id.g45fc438f8d_0_2918 )