Blocks that cannot stand without support and that do not have a bug MCPE-139010 can be placed on a light block. Exceptions are plants that require dirt or some other block only.
Steps to reproduce:
- Place the light block.
- Place a block next to which you will aim to place the block (the generic block is leaves. Most blocks that need support are not put on it).
- Pick up the block that requires support for placement (excluding blocks from MCPE-139010).
- Aim at the support block and place the block on the light block.
The light block can be used to place blocks that require support for placement.
The light block should practically not interact with the world in any way.