The Standard Command Toolbar is a subset of the toolbar that is shown if the corresponding checkbox in View->Toolbars is checked. It has a number of standard commands the extension can support. If the extension in the currently active panel supports any if these commands, the commands will be enabled; otherwise they are disabled.
Button 1 refreshes the content in the active panel.
Button 2 cuts the selected content to the clipboard.
Button 3 copies the selected content to the clipboard.
Button 4 pastes the clipboard into the active panel.
5. Resize Panel
Button 5 provides a dropdown list from which you can select how you want to split the panel. Clicking on the icon itself reverts to a 50/50 split.