oh okay sorry
i think the best is to create a scene or composition which is deactivate
but make them appears smoothly is difficult. Smode calculate a shaders chain before display the final render.
if it's blink by default, smode won't calculate it and will start the calculation the moment it appears.
It have to be done once. After that, Smode remember the shaders chain and activating/deactivating a layer become a smooth action.
I don't know if it is your case, but it seems that you want to create some visual in live. If it is, here is my advice:
You Have 2 NDI Connected PC's: one for some creation and the diffusion, another for the creation in live. Send the rendered composition through NDI from the second one to the other one.
Hope it helps you