Not to my knowledge.
You could make an alias that performs the /toolbar commands to create the buttons, then call the alias from an on start event, or just put the commands into an on start event.
The advantage to having an alias (possibly) is that you can always call the alias manually to re-load the toolbar buttons.
You might think about posting this suggestion in the Feature Suggestions section, as I can see how people might be wanting something like this now that the toolbar can be customized.
