I did an expanded code sample to try your method for passing a 'Nothing' parameter:

loText = CREATEOBJECT('CodeMax.TokenSet.4')
WITH loText
.Id = cmTsIdText
.Name = "Text"
.ValidScopes.Add(loScopeKeywords)
loInterface = GETINTERFACE(.ValidScopes,'ITokenSets')
loInterface.Add()
ENDWITH

It would execute, but the desired effect did not occur (had additional TokenSet defines and set the scoping of each). The scoping of each TokenSet was not set as needed in the Add method. Additionally, when closing the form in VFP, VFP crashed (possibly something hanging in the ActiveX).

I have solved the basic problem using the other option of defining the layout in XML and then loading that.

Thanks for your help.