As models grow, it’s easy to accidentally create new elements with the same characteristics as existing ones, instead of re-using existing elements.
Now Model Expert can show you these duplicates, and help you to fix them.
Duplicate elements are ones which have the same type, stereotype and name, and having duplicates is not necessarily an error.
For example, process models may have lots of Gateway (decision) elements with no name. Or, your project may allow the creation of duplicate elements so that projects don’t interfere with each other.
…but in all cases, it’s good to understand where you have duplicates, as un-wanted ones can cause problems if they are not fixed.