This should be in the Creo forum maybe Toby Metcalf can move it.
Anyway, you can create datum points on the line segments with a ratio of .5 to place them at the middles of the line segments. Alternatively, create datum axis points in the original sketches that are at the desired location so they will be available to make this measurement.
I agree with your answers but again these datum points will serve only measurement purpose and may increase model tree. If model is open by another person in future and in case he/she highlight datum points there are few chances that he will understand the purpose of these datum points. And in case if he conclude that these datum points do not have child feature they will become an unnecessary feature for him also it increase the model tree which will impact CAD model regeneration time. Let me know your thoughts.
As a workaround if the parts are symmetric, you can use the surface to surface measure at the ends as shown that gives the same result as the center to center measure.
I agree with all of your suggestion. They are very helpful. Apart from that there is one thing that it would like to highlight I am not sure whether it is proper place to say it or not, but It will be very helpful and great if PTC will improve "Measure Summery Tool" in Analysis tab to measure Center to Center distance between two unsymmetrical feature (like twp ribs, or walls etc.,...) as shown in attached snap shot to discussion subject.
