To create a button for the main toolbar is the easy part....
1) Go to menu "Tools" and then "Scripts" (or just press F9)
2) Click on "buttons"
3) Add a script (to write one is the harder part...) to the desired button (e.g. #1).
4) On the right hand name choose a description for the yellow tooltip that will appear when hovering the mouse over your button.
5) Close the scripts window
6) Go to menu "Tools" and then to "Customize" (or press SHIFT-CTRL-F7)
7) On the left hand side, select "user action 1" and move it to the right hand side. (for whatever reason it is called "user action", instead of "button" ???)

Close the window.
==> Et voilà, there is your circle button #1.
Hope this helps at least partly...
Adi