Illustrator won't let you add custom command buttons to the Control Panel bar running horiztonally across the top of the workspace. That bar remains clear because the items on it change depending on the tool that is in use and/or the object(s) that are selected. The Application Bar (containing the File, Edit, Object, etc menu commands) doesn't allow additional tools to be added either. You can add columns of custom tools or tool bars on the left and right ends of the work space. If you have a multiple monitor setup you can even float tools or toolbars onto another monitor as another option to keep them out of the way of your artwork.
Hi @livl17017666, I'm not familiar with the SDK, but another option is to make a simple CEP panel with the button. It would behave like any other panel so you could dock it wherever you can dock panels. The button would run a script.