Motion tag for falling block slows down

Solution 1:

Try This Command:

/summon fireball ~ ~ ~ {ExplosionPower:0,direction:[1.0,0.0,0.0],power:[1.0,0.0,0.0],Passengers:[{id:"minecraft:falling_block",BlockState:{Name:"minecraft:sand"},Time:1}],Item:{id:"minecraft:sand",Count:1b}}

It summons a falling block riding a fireball which travels infinitely (I think) It won't look just like a block but you can adjust the item for the fireball and the block for the falling block. You can adjust the power and direction tag for movement.

Made using: https://mcstacker.net/

Idea two:

/summon falling_block ~ ~ ~ {NoGravity:1b,Time:1,Motion:[1.0,0.0,0.0]}

No Gravity tag should prevent gravity effects from being used. Which could have been stopping the block?

Giant Idea:

/summon giant ~ ~ ~ {NoGravity:1b,Silent:1b,Invulnerable:1b,NoAI:1b,Tags:["TPme"],ArmorItems:[{},{},{},{id:"minecraft:sand",Count:1b}],ActiveEffects:[{Id:14b,Amplifier:1b,Duration:999999}]}

or

/summon armor_stand ~ ~ ~ {NoGravity:1b,Silent:1b,Invisible:1b,Tags:["TPme"],DisabledSlots:4144959,ArmorItems:[{},{},{},{id:"minecraft:sand",Count:1b}]}

Repeat:

/execute as @e[tag=TPme] at @s run tp @s ~0.1 ~ ~