I'm going to assume that this allocation is via a 401(k) at work and you only have so many options available to you, otherwise I don't know why you'd pick those when you could get ERs through other Vanguard products 6-8x lower. If you actually do have choices, then ditch those things and get cheaper stuff. You like large cap stuff, like VWNFX? Ditch that, get VTSAX, 0.05% ER. Can't afford the "admiral shares?" Get the ETF version (VTI), only slightly more inconvenient because you can't buy fractional.

You say you started contributing in '06, I'm also going to assume you've been maxing every year because otherwise you probably don't have enough in there to the point where even a horrible -40% drop in a year wouldn't just get immediately offset by your year's contribution. Play around with the included link (you find that certain assets don't go back far enough so you have to find something roughly equivalent, which isn't too hard for the index-trackers like you have). Set your starting time to like the worst possible time, like a month or two before the start of the last 2 big crashes. You'll see that it's not really a huge deal, especially when you're not going to retire for another 30 years. Most of the people who got in major trouble solely on their investments (getting laid off doesn't have anything to do with bad investments other than exacerbating their negatives) were ones who had 0 diversity--even if you picked just 1 single index fund like VTSAX you'd be far better off than them)--or they picked individual stocks themselves, or they were trading on margin or whatever. Those last 2 points, the vast majority of people aren't smart enough to pull that off with sustained success and the ones who are already know it, and don't need to ask other people for advice.

Also like Hokie360 points out below, your exposure to bonds is enormous for how far off your retirement is. I'm going to spin things another way on you: investing since '06 at that allocation, the gains you've already missed out on are probably larger than anything you would've lost in a reasonable market downturn. When I say reasonable, I mean 40, maybe 50% retracement. Frankly if you have anything worse, some hypothetical 70% retracement, that's going to be like crossing the Rubicon man, retirement is going to be the least of your worries.

I absolutely guarantee you that if things start looking that bad, no matter how good or bad you think the policy is, you're going to see direct participation in equities markets by the Fed. Not like QE where the Fed is scooping up Treasury bonds, I mean they'll be buying shares of Amazon and Ford and Pfizer directly. And just for fun let's say all the most unconventional financial tactics fail. Direct market buys. Negative interest rates. Helicopter money. At that point, you're going to start looking at things like war, a USSR-like collapse of the government, some really bad stuff. Your retirement account isn't going to save you from that; you either already have enough money for that, or you won't be able to acquire enough unless the apocalypse is like 50 years away. And if it's that far off, by the time it shows up, you can always just kill yourself, you'll already have lived most of your natural life anyway.

So all that said, relax. If you try to time the market and quick shift into cash in the downswing, and then buy sort of near the bottom, you're going to mess up. You'll panic too early, sell off into cash, and then whoops the buy-side restrictions will hit you and you can't go back into your funds for 60 days and miss 2 months of gains. Or you'll sell after a 20% drop but surprise the bottom was at 23%. Or maybe you'll sell at a 20% loss but it really was a 50% bottom, but you don't care now because your company got hammered and you got laid off and so did everyone else and now the job market is again flooded with applicants. Or whenever you sold off, even if it was close to perfect, you sold at -5% ahead of -30%, you're going to wait too long to re-enter. Everything's going to look like a bull trap or a dead cat bounce, and by the time you have confidence to buy in again after selling, the differential between what you did, versus just leaving it alone and continuing business as usual, is probably not very big. In fact, in the time and mental/emotional energy spent trying to perfectly optimize this scenario, you probably could've been spending time with friends or family or otherwise enjoying life and not worrying about whether you managed to prevent 20-30k worth of losses back in 2019. The good news is that if your brain is screwed up enough that poring over spreadsheets and charts sounds like more fun than going for a walk or playing with your pets or spending time with your friends, then congrats you might actually have what it takes to successfully make your own trades in the market and you can make tons of money naked short selling all the way to the bottom of the crash while taking on tremendous levels of risk.