Overview
mojoPortal uses specific toolbar names in all the editors, so you can't change names of the toolbars or add arbitrary ones but you can customize what is on those toolbars.
TinyMCE Configuration
To configure toolbars and plugins for TinyMCE, copy the file mojoTinyMCE.config from the root of the web site. Rename your copy, then change this setting in Web.config/user.config to point to your custom file.
<add key="TinyMCE:ConfigFile" value="mojoTinyMCE.config" />
The file is an xml file that can be edited with a text editor.
CKeditor Configuration
To customize CKeditor, copy the file from yoursiteroot/ClientScript/ckeditor-mojoconfig.js, rename your custom copy, then point to your custom file using this Web.config/user.config setting.
<add key="CKEditor:ConfigPath" value="~/ClientScript/ckeditor-mojoconfig.js" />
FCKeditor Configuration
In mojoPortal the FCKeditor configuration file is at /ClientsScript/mojofckconfig.js file. However I don't recommend customizing that file directly. Instead, copy it and rename it and then change this setting to the new file. You will find this in Web.config but ideally you will override it in user.config
<add key="FCKeditor:CustomConfigPath" value="~/ClientScript/mojofckconfig.js" />
If you were to just customize mojofckconfig.js directly, you would likely lose your customizations next time you upgrade because the new file would replace the old one. By using your own custom named file you can avoid this.