I understand what you need to do. However, this wouldn't be possible, because only the custom controls are saved in the configuration files and the default ones aren't present there. If they were, you would only have to change the order inside the .config file and the position inside the toolbox would be changed, but for now this cannot be done.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items