Have you incorporated Vecna more into the campaign and if so how did you do it? Looking to improve the campaign.

Our group has tried several times to run a 1-20 campaign that always seems to fall short. This time we’re making really good progress but we’re finding this campaign slipshod and a hodgepodge. We’re near the end of The Lambent Zenith, completely RAW so far, and I’m planning on home brewing a bit. I’m likely scrapping/reflavoring the Eberron chapter to Exandria to work in more of our prior campaigns. I’m making a note to let them research more in Sigil and maybe bringing back some old PCs. I’d like to work in Vecna more, make the story more cohesive. I’ve seen various posts on this before but am having trouble finding them again. Have you made Vecna more prevalent in your games and if so how?