This is a complaint and a workaround I ran into with the Trace Network. First I want to say this is great and looking forward to more from this new functionality!
I have found that adding points when clicking on the map is very slow (sometimes, not always). If I wait a long time (30 seconds) the point shows up. I have a workaround however, if I select an feature and click the other button (Add selected) that works instantaneously.
Just a report for the trace network team.
Thanks again for the tool @JonDeRose -- clearly your team has been re-imagining the interface with the Pro design in mind and it's looking quite "Prothonic" to me (that's a compliment) as I convert old Geometric Network tutorials to the new tool.