If you are the custom dropdown inline in the <tools> tags of RadEditor, this will reset the toolbar. In such case you can declare manually the rest of the toolbar tools.
It would be much easy to use a ToolsFile
and add the new tool to it. You can download the default toolsfile from this article: http://www.telerik.com/support/kb/aspnet-ajax/editor/default-toolsfile-xml-file.aspx
You can find more information about the toolbar and the custom tools in thes articles:
the Telerik team
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