Why would you need to mod your inventory when there's creative, you can switch from creative back to Survival.
There are blocks that creative mode doesn't give you still, Portals, Lava sources, Water Sources, possibly sponge I don't remember checking for that since i presume it won't affect the water, thoi I hope I'm wrong about that... anyway, that's why I think. I'm interested to know if anyone has updated a tool to work after this patch too tbqh.
Sponge is in decorations, and about the portal and lava and water, why not just use the buckets and obsidian for the time being? Maybe it will get a fix but not exactly sure, the only thing missing is the mob spawners.
So it is :-[ and you're right for sure, I'm in the quandry of being a lazy turd who wants at least one 128x128 square of lava in a flat nether tho and buckets are making me question my sanity (QQ) - I guess it'll just be a more gradual development than I'd hoped! Patience is a virtue and all that... On the spawners tho, I think if we spawn them they'll probably spawn pigs, but a steady supply of effortless cooked pork is not bad thing, sucks for the pig I guess, oh well! I'll keep an eye out just the same and if I find an editor that works with the update I'll reply here with a link