How have all the elements in the universe been created?
There are two classes of elements in the universe - those that occur naturally and those that are man-made.
The first class of elements comprises elements 1-92 on the Periodic Table and all of those are already created.
The man-made elements consist of those from element 93 to about element 120. These elements are made by taking smaller atoms and smashing them together at very high energy so that in some cases the smaller atoms fuse to form larger elements.
As scientists learn how to do this atom smashing with larger atoms and higher energies they expect to continue to create new elements. So it is likely that there are still more elements yet to be created. But understand that when creating these new elements in most cases only a few hundred atoms may be formed of the new element and that most of the new elements almost immediately breakdown again because they are not stable.