Don't want to write this by hand? GodCraft sets minecraft:can_stand_on_powder_snow for you with a switch.Get GodCraftOverview
minecraft:can_stand_on_powder_snow is an entity component: it goes in the components object of a custom mob, or in one of its component groups. Lets the entity walk on powder snow without sinking into it.
Example
Inside the components object of BP/entities/<name>.json (values are the defaults or placeholders):
BP/entities/<name>.json
{
"minecraft:can_stand_on_powder_snow": {}
}