My creativity is infinite by not having a way to sit down and by not having vertical slabs. There's no way in the game to do these things no matter how creative you are. A trap door is (usually) not a substitute for a vertical slab and and there's literally no way to simulate sitting down. That's Microsoft saying they don't want to, it's nothing to do with us. And that's just the top two things on their rejected page.
@Advocate I think the slabs may be a technical limitation. They'd have to deal with every combination of top & bottom slab, which might involve tons of new blockstates or an overhaul of how slabs were handled and thus not be very feasible when they have other things to work on.
Or it might be another vertical slabs thing where they say it "liMitS CreAtIViTY".
Biome specific dungeons for every biome to make core mechanics less esoteric for new players.
Before you go on and say "these will litter the world." Each one will spawn in 10,000 blocks away from each other and make sure its not the same dungeon until over 60,000 blocks in all directions. These dungeons will all be roughly the size of woodland mansion and ocean monument. The player will need to buy maps from the cartographer.
I'm not going to have ideas for each biome but I will give some solutions for some biomes. The plains temple will go over all about farming, breeding and maybe taming puzzles, and have the aesthetic of an abandoned american barn. You can learn how far one water source block can reach farm land and get a key. In the next rooms you will find randomly generated puzzles. One can be a sheered sheep in a room with a fully dirt floor with no grass, and it asks you to bring a grass block to regrow its wool. Another room can have one animal and a lead or leading food to teach the player to take it to another room to breed the animal.
Another biome dungeon can have a main room where it tries to teach the player how more bookshelves will power an enchantment table. Of course the player has to bring the enchantment table. There the puzzles will center around certain enchants with veins of lapis in the walls. Another dungeon will be all about potions that center using potions. Another can teach about beacon effects. One can teach fireworks boost the elytra with rings to go into. One can teach about parkcore.
You will need to bring external things to help you but in each dungeon you will receive the puzzles required solutions, the dungeon will make it very clear what the main puzzle componet will be for new players some how, how im not sure. You will also be able to get keys for locked doors. At the end of the dungeon theyre will be a mini boss that tests the knowlege of the temple and when defeated will give you a loot bag of dungeon loot. You can also respawn these mini bosses with a craftable similar to the end crystal. I feel the woodland mansion is a good enough dungeon for combat learning. And the ancient city is good at teaching redstone. The stronghold will have combinations of dungeon room puzzles to make sure they have a good enough knowlege to fight the ender dragon.
The potion of rebounding is a new portion that requires an echo shard to brew; this is unique from the other potion types as to observe it's effects you'll have to wait for the effect duration to end.
Basically drinking this potion at a particular point turns that spot into a 'save point' and after the potion effect runs out you get teleported back to the save point location.
Drinking milk with this potion effect on you teleports you back to the save point location whenever you desire making it very useful for quick escapes, mimigame shenanigans and would be a great tool while exploring large structures like the woodland mansions, ancient cities, ocean monuments and strongholds to stop you from getting lost in these structures.
This can also be found as an uncommon loot type in the ancient cities chest as well.