AFAIK, there is currently no accepted/conventional treatment for WSS.
The question suggests not including what amounts to "lifestyle" treatments. This is absurd on the face of it and I will not follow this suggestion.
For example, currently, in the U.S. where I live, the single biggest thing people die of in our society is poor lifestyle choices. Existing science is particularly clear on this point. Nevertheless, the "medical" community, for the most part, is ignorant of this reality. A big part of the reason why is that most doctors are mostly ignorant about what I like to term "lifestyle science". If you are ignorant about this, or find what I say difficult to credit, please see NutritionFacts.org -- Michael Greger's marvelous science-based web site about lifestyle science. Or see John McDougall's https://www.drmcdougall.com/ website. Or see T. Colin Campbell's nutritionstudies.org website. Or see Caldwell Esselstyn's www.dresselstyn.com website. Or see Neal Barnard's www.pcrm.org website. Or see Dean Ornish's https://www.ornish.com website. Or see Joel Fuhrman's https://www.drfuhrman.com website. Put bluntly, we are needlessly dying and suffering because our medical establishment and what passes for healthcare (it would accurately called sick care) is dysfunctional, corrupt, and not based upon current science, not oriented toward prevention, and not based upon sound public policy (please excuse my tirade).
Personally, I suspect a nutritional intervention may help individuals with WSS. And I have begun trying it out on my son (unfortunately not until many developmental critical periods have already passed, since I only recently discovered my son has WSS).
We know/believe that the the WSS gene codes for a protein catalyst involved in the epigenetic machinery/metabolism, in the histone metabolism is part of how epigenetics works. We suspect this damaged catalyst simply fails to function correctly as a catalyst. Since typically another, fully functional gene typically exists on the other chromosome in WSS-affected individuals, the net result is abnormally/unusually low level of functional catalyst -- we think that this is how the deleterious effects of WSS may manifest.
If this is true (and we think it may be), it may be possible to boost the levels of functional, non-damaged, catalyst in WSS individuals by boosting the level of catalyst precursors, and that this may be done nutritionally by boosting sources of folate and related nutrients in the body.
Now this is all somewhat speculative, and therefore not an entirely risk-free approach. Nevertheless, it may prove beneficial since it amounts to simply feeding WSS individuals extra greens.
There's a couple things to be aware of regarding this speculative nutritional intervention.
First, and most importantly, even if this speculative nutritional intervention turns out to work, it MUST be started early, perhaps even prenatally by the pregnant woman carrying her WSS fetus eating copious amounts of greens. Of course, this should only be done with your OBGYN's supervision, but since most doctors are pretty ignorant about nutrition (see above), good luck finding an OBGYN that isn't. The later you start, the more developmental milestones will have passed.
The second thing to note is that boosting consumption of greens is something that should be done for the vast majority of infants, toddlers, and children in the U.S., since the population for the most part is grossly undernourished with respect to consumption of greens, in any case (again, see above) -- even when WSS is not present.
Third, as I mention previously, though this "treatment" may consist of simply feeding affected individuals greens, and even though many babies/toddlers/children currently don't get enough greens, there nevertheless may be risks to this approach.