VXF
Vanguard Extended Market ETF
stock NYSE ETF

VTI is the total stock market of the US, cap weighted. And VXUS is the total stock market of the work (minus the US), cap weighted. VT gives you the total stock market of the world (VTI + VXUS), cap weighted.
VOO is the top 500 stocks in the US, cap weighted (s and p 500). On the other hand, VXF is the US total stock market excluding the top 500 stocks in the US, cap weighted (so VTI - VOO). So VTI is basically VXF + VOO, cap weighted.
So what you want to realize is that sometimes large caps do better than small/mid caps. Sometimes vice versa. Sometimes the US does better than international. Sometimes vice versa. Those trends can last years, but not a lifetime.
So your risk-adjusted best bet is to just invest in the total world stock market, cap weighted. Then as various parts of the world or market do better, they grow and become a more significant part of your portfolio over time, and parts that do poorly gradually become less of your portfolio.
No management required.

Another fund to maybe consider is VXF. This fund is designed specifically to be a perfectly fit for people who already have VOO.
(Compared to VB, VXF also has mid size companies, not just small companies.)

You may want to check out $VXF; I've really liked that recently. For international, $IDVO is a surprisingly stable core that produces income while also preserving growth. $AVDV/$AVES are a bit more expensive but they're actively managed, & $VSS is an international small-cap catch-all. Thanks for letting me share so much! I'm definitely in the international camp as a hedge just in case...

Dividends are for when you’re closer to retirement so I would get rid of SCHD altogether. VTI is about 80% VOO, so that’s kinda redundant. If you want to have American companies outside the SP500, consider VXF

For an investor like yourself who already owns VOO/VXUS, here are a couple of obvious suggestions:
VXF would give you the rest of the US stock market (small and mid sized companies) that are missing from VOO. Basically, VOO + VXF = VTI.
BND gives you the US bond index, if that is something that appeals to you.

I have not used the Fidelity Zero Funds (*no fees at all*) even though my accounts are parked at Fidelity. I'm just curious if anyone has a 5-year or longer position with any of them? When compared to the closest counterparts, they seem to track almost identically.
FNILX: US large cap (\~VOO)
FZROX: US broad market (\~VTI)
FZIPX: US small & mid cap (\~VXF)
FZILX: International (\~VXUS)
Diving further into Fidelity's offerings, their S&P 500 mutual fund (FXAIX) and their total US stock market mutual fund (FSKAX) have an extremely low ER of 0.015% each. I don't have either, but they are worth mentioning.
Does anyone use any of these in their portfolio?

the easiest way to start is buying the whole market instead of trying to pick individual stocks.
a lot of people just use low cost index funds to match global market capitalization weights. you can do this by mixing funds like VOO (U.S. S&P 500) and VXF (U.S. Small/Mid Caps) for domestic coverage, and pairing them with VXUS (Non U.S. International Index) for everything else.
setting up automatic transfers makes it hands off. you just let the market run over the long term.

It is easy but hard business. Keep VOO to 45% add VXF 15% and add VXUS 40%. Check VT breakdown on Jan 1 every year copy the info put that in VTI and VXUS. Just keep emotions in check and you will do fine. Excessive emergency fund will help take use of crashes but you still contribute your own way crashes just icing on the cake and have long life my hero Jack Bogle. 

Well imo opinion you have pretty much won at investing.  The only thing I would offer is look into global diversification.  Add in some VXF, (US Small/mid size Index). And VXUS (Non US, International index).  But only if you want to.
Your doing good. Remember to not sell if the SP500 crashes/corrects. Just let it recover and keep on buying.