AFAIK, the “rule” for what gets included as a Top Bar passive (the noticeably smaller boxes next to the larger ones that you can click) seems to be that it’s global, and works without requiring any setup nor user input (prestiges and other conditions aside). So the actual ones include: Karax’ Chrono Field and Reconstruction Beam; Vorazun’s Strike From The Shadows and Emergency Recall; and Artanis’ Guardian Shell and Warp Harmonization.
And perhaps also tack on that it works for both you and your ally (Warp Harmonization would be an exception)? Does it feel like others should’ve been their own “small box”? Namely…
—Abathur’s lv13/Locust Injection - Enemy units have a chance to spawn friendly Locusts upon death.
—HH’s Salvage - It’s their lv1 talent, but works for both players
—Stukov’s infinite Creep Spread.
… Stukov has the infinite creep spread ability listed for his Infested CC. IIRC, HH and Aba have their things listed elsewhere as well. Does it feel like it could’ve been explicitly lasted in their top bars as well?