How can a custom attribute be added to a "markup object type" saved with CreoView in Windchill?

Hi @Emrec@n , and thank you for your question. 

I recommend giving more details and context about the problem you have in mind. Specifically, it is important to think about the use case: what you are trying to accomplish in context.

Please refer to this guideline to make your questions more likely to receive a quick and useful answer.