>>One cannot do it in design mode. Exit Design Mode first.
>
>I could not figure out how to do this, so I exited Excel and re-opened. Now I can change the status.

For Exit/Enter Design Mode there is an icon on the VB Toobar, and on the VB Control Toolbox: looks like a green trianle and with a pen.

>
>The other question - if I want to make the whole column to be checkboxes, should I somehow use copy/paste approach?

As usual in Excel: select the cell with information you need to copy, Copy, then select the range you need to paste information in, and Paste.