Float Minecraft Sand and Powder Concrete?

Is there a gamerule or command where sand gravel etc doesn't fall off?

I don't know of any. Maybe with plugins…

You can put a thread under it, you can hardly see it and it works.

Well, not really. You can only more or less suspend gravity, but then the blocks will just become floating entities. For this you already need a modification or a plug-in.

You can use strings or barriers that line textures from non-falling blocks to the texture of sand or dry concrete, or you can place a non-falling block and create a falling block with McStacker that looks like sand and doesn't fall off.

-Sand---

- bouquet of roses ---

-Block of your choice ---

in sequence the whole

Remove block of your choice and tada

Ne does not work in 1.15.2