Greetings,
A Feature Dataset(FDS) can have more than one topology. That being said, Feature classes(FC) can only participate in one topology at a time. I ran the following the experiment to test it out. I had a line FC and a polygon FC in a FDS. Then I created a topology and both of those FCs participated in that topology. I then attempted to create a second topology. Pro did not allow me to complete the dialogue because they was not a FC that was not already participating in a topology. I then added another FC to the FDS. Then I was able to Create another Topology and that third FC was the only FC Participating in the second topology. I hope that helps. Thank you for everything and have a delightful day.
Sincerely,
Joe Guzi
