One of the initial consequences of the periodic table was that the gaps were correctly seen as suggesting the existence of elements that had not then been discovered (or made, of course) and as a guide to their chemical properties, which was useful in finding them.

I think it is clear what question is being asked here. There will be a limit on the maximum size of a nucleus stable enough to count as an element, as there are a couple of effects which, at some point, will be insurmountable (and which are also responsible for an isotope of lead being the largest stable element.)

One is that the electrical repulsion of the protons is long-range, while the strong nuclear force binding the nucleons together is short-range. To simplify quite a bit, in a large nucleus, each proton is being repelled by every other one, while it is being bound only by its neighboring nucleons.

The second effect prevents this being worked around by adding more neutrons, as one reaches a point where it is energetically favorable for a neutron to convert to a proton via beta decay.

As mentioned by others, there is likely an 'island of stability' around the largest elements created so far, but this is, at best, only a brief respite from the inexorable effects described above.

The estimates of the half-live of any given element on the island of stability ranges over several orders of magnitude. That being so, it seems unlikely that there is any clear idea which isotope is the largest possible in this universe.

Neutron stars are, of course, very large agglomerations of nucleons, but it seems pointless to call them elements (and there is an upper limit on their size, anyway.)