The other thing you can look for is what is sometimes called a Stable Value fund. We were using Utah before PA for S24, and it looks like they have changed things around some since then, but they have the PIMCO Interest Income Fund, which is a stable value fund.
SV funds are very boring and won’t always keep up with college cost inflation (like the GSP should). But they also didn’t drop like bond funds when interest rates increased. So, like, that SV fund had a 3-year annualized return of 1.87% as of end of 2023, which is not great, but it beats the 3-year annualized loss of -3.32% for the Vanguard “total bond” fund that Utah also offers.
That said, I think this was a much bigger risk back when bond rates were so historically low. At today’s more normal bond rates, I think you could do a short-term bond fund if available, or maybe a mix of a total bond fund and FDIC account if a short-term fund is not available.
Or probably just use your age-adjusted fund’s terminal portfolio. Like Utah has a target enrollment fund, and their Enrolled portfolio is 45.7% Total Bond, 8.30% Total International Bond, 20.25% Stable Value, 15.75% FDIC, and 10% stocks. That 10% makes very little practical difference, and otherwise that is actually not notably different from what I was suggesting (which is because I am not coming up with anything particularly clever). They are apparently trying to juice returns a little (probably to keep up with college cost inflation), which is a little risky, but these days I would not see that portfolio as excessively risky.
Edit: By the way, I sort of promised simple, and this is not so simple of a discussion!
So here is pretty simple. I think a very solid plan is use their target-enrollment or age-based option, contribute early and often, and then withdraw as qualified expenses arise.
And then try to ignore yearly ups and downs.