Создай сущность:
kill @e[type=minecraft:armor_stand,tag=bridge]
summon minecraft:armor_stand x y z {Tags:["bridge"],NoGravity:1b}
Цикл:
execute at @e[type=minecraft:armor_stand,tag=bridge] if block ~ ~ ~ minecraft:air run setblock ~ ~ ~ minecraft:stone
(Цепной, УСЛОВНЫЙ): execute as @e[type=minecraft:armor_stand,tag=bridge] at @s run tp ~ ~ ~1
execute as @e[type=minecraft:armor_stand,tag=bridge] at @s unless block ~ ~ ~ minecraft:air run kill