Anything like runtime ids for blocks?

[hard trail]

Or can I add or edit vanilla block states?

I'm trying to make blocks that are replaceable like air, tall grass, snow, sculk, etc. but without block events. Several questions have asked already but the only usable solution has been block interactions to register held items and then then replace the block with the item. Many blocks have this effect and I think it would be much simpler to use existing blocks. Is it possible to edit vanilla blocks or give custom blocks vanilla block properties?

[fierce sandal]

The only vanilla block states custom blocks can use are minecraft:cardinal_direction minecraft:facing_direction minecraft:vertical_half and minecraft:block_face

There isn't a built-in way to make your block replaceable. I think the best solution would be scripting