Short answer: CoQ10 and psilocybin each have early evidence pointing to effects on inflammation, oxidative stress, and stress perception, but neither is proven as a treatment for rheumatism. Small studies suggest CoQ10 may support markers linked to disease activity when added to standard care. Psilocybin research is mostly in adults and focuses on mental health; any effects on rheumatic symptoms remain unconfirmed.
Combining them has not been studied. I cannot verify any synergy or added benefit from using CoQ10 before a psilocybin experience. If considering this, discuss it with your rheumatologist and pharmacist, since interactions with DMARDs, biologics, corticosteroids, NSAIDs, anticoagulants, and serotonergic drugs are possible. Psilocybin has legal and safety considerations and is not for minors or pregnancy.
If you want a general introduction to what a guided psilocybin session involves, see this overview. For now, treat the combo as a hypothesis and prioritize evidence-based care.
Hope this clarifies your options.