They can't pack up WDW and move to another state, but they can relocate DCL home ports, slow/stop construction of new hotels in FL (and prioritize new DVC builds in CA over FL, possibly with more Hilton Head type beach resorts outside of FL), and move office workers to other states. None of that would equal the impact of moving all of WDW, obviously, but it's not nothing, either. I'm sure Disney would prefer to have the courts rule in their favor over those options, though.
For DCL, Florida is probably the best location, mainly because of its close proximity to Castaway and the new Lighthouse Point private islands, but also WDW. South Carolina or Georgia
might be a reasonable re-lo option for them but those aren't great ports, and would require some major investment to get up to standard. Of those two, Charleston might be the better option, since no major cruise lines go out of Savannah. Also, compared to WDW, the cruise ports don't employ near as many people, so the impact there would be small, but certainly significant for the areas, although, I think the other cruise lines would quickly absorb them, so it wouldn't be a big loss for the state. The biggest hit Florida might see with DCL pulling out would be in tax and tourism revenue, but again, those might be leveled out by other cruise lines.
Building more DVCs outside of Florida also wouldn't have a big effect, as those outside Florida, don't have as big a draw, with the exception maybe of Aulani.
The other option was the suspension of the Lake Nona project, which was in progress. While this wasn't a large impact to the area, it was an investment and would have likely meant more jobs and revenue for the area in the long term. The bad part about this for Disney is that it would have been a significant savings for them. There really isn't another location for them to move to that would have the same cost benefit as Florida.
Outside of these, they could suspend or slow development in Florida, but that will hurt them more than the state. Sadly, they seem to be over a barrel here. Theirs and Florida's best bet would be for this to be settled and a return to what they had or something similar.
One other option would be for them to get REAL political and dump a bunch of money and advertising against Desantis. They could also donate heavily into his opponents, but as we've seen here, that can cause backlash as well with their fan base. If I were them, I would at least go on a publicity tour maybe with some advertising and perhaps even trying to get some other Florida business leaders to help them fight back. At the very least, hire a PR firm to help them wage this battle. It might be costly in the short term, and the timing couldn't be worse for them to incur such an expense, but losing this fight could also be costly for years to come.