Sorry David. That functionality is not available.
This isn't fully supported because your changes will be lost when you upgrade etc. But you can control which options are available in global succession by editing the web.config file in your Reg app. You can remove the spec type specific <SuccessionSpecType> nodes inside <SpecTypeMappings>.
For example, to turn off Material Specs remove the <SuccessionSpecType type="1004" ...> block
Hope this helps,