Place a Sith Holocron next to Snoke on the left armrest of his throne.

You could add it to the entirely of TLJ, or at the very least his first scene with Kylo Ren. It’s a small detail that doesn’t necessarily spell out anything, but it could add an extra clue regarding Snoke.

Snoke could’ve been a dark side acolyte or enthusiast who used the knowledge of that holocron to gain his power. He could’ve been an already powerful dark sider who used the holocron to unlock new secrets. He might want to restore the Sith Order, or is just using it for his own personal gain. Or, it was left by Palpatine to manipulate others as a part of his contingency.

Still keeps him mysterious, but at the very least it gives us an onscreen source of his power for those who feel like there wasn’t enough. The desire for such an addition might change if we learn more about him in IX, but if we don’t I think it would be a pretty simple idea to implement.

While it would take more work, if you added it to all the throne room scenes, you would also get a nice bit of dualistic imagery when the Sith holocron rests on one side of Snoke, and a Jedi lightsaber rests on the other.