Hi Falk,
In order to achieve your scenario you should open the \Program Files\Common Files\Microsoft Shared\web server extensions\wpresources\RadEditorSharePoint\
4.x.x.x__xxxxxxx\RadControls\Editor\Localization\<
Used_Localization>\Help.ascx
file and edit it so that it only contains information about the desired editor's tools.
Save the file and reload the page with the editor to see the updates.
Best regards,
Rumen
the Telerik team