I think what you're asking about is the fact that your taxable account will be 100% equities, even though your overall assets have the appropriate proportion of bonds. Your overall asset balance will be stable, but your taxable account balance will fluctuate wildly with the market. You're trying to come up with a tax-efficient way to stabilize your taxable account.
Is that it?
The answer depends on your income level in retirement. If your retirement income is high, or potentially high, you can use municipal bonds in the taxable account. This counts as tax-efficient bond placement.
A better answer may be the one provided above. Go ahead and place bonds in the taxable account. Bond returns are so low that it takes quite a bit of them before they impact your taxes. You might be able to use just enough to keep your taxable account balance stable, while staying below taxable thresholds. Keep in mind, though, that while balancing in your tax-advantaged accounts has no tax consequences, attempting to balance in your taxable accounts does. Specifically, if you sell stocks to buy bonds, you may get capital gains taxes. (Selling bonds to buy stocks may also incur capital gains as well, but since they move so much slower, they're not as much of a consideration.)