Presumably if one is retired, then one is not 100% stocks/equities. So if equities drop, one simply rebalances by exchanging from fixed income assets (bonds!) into equities to get back to one's desired asset allocation.
And one only has one portfolio. Not a taxable portfolio. Not a tIRA portfolio. One portfolio possibly made up of several accounts: tIRA, Roth, taxable, whatever.
If one isn't buying equities after substantial drops, then one ain't doing it right.
If one has to pay expenses, then one sells something, but should always rebalance back to their desired asset allocation.
Also consider that a retiree with a 60/40 asset allocation and withdrawing 4% a year, sort of has 10 years of assets in fixed income.
This is not rocket science, brain surgery, nor rocket surgery.