If you use this command
/give @p minecraft:armor_stand{EntityTag:{NoGravity:1b,Passengers:

{id:"minecraft:armor_stand"}

}} 1 [all right side Minecraft 18w16a]

in the theory it give me a Item. With that I can summon armorstand riding on a armorstand, but it doesn't work
I don't know why

Console outeput:
20:25:58 net.minecraft.server.MinecraftServer Saving chunks for level 'Copy of New World'/the_nether
20:25:58 net.minecraft.server.MinecraftServer Saving chunks for level 'Copy of New World'/the_end
20:25:59 m Loaded 133 advancements
20:26:01 dbc Saving and pausing game...
20:26:01 net.minecraft.server.MinecraftServer Saving chunks for level 'Copy of New World'/overworld
20:26:01 net.minecraft.server.MinecraftServer Saving chunks for level 'Copy of New World'/the_nether
20:26:01 net.minecraft.server.MinecraftServer Saving chunks for level 'Copy of New World'/the_end
20:26:34 net.minecraft.server.MinecraftServer [Vinctilus: 1 [Rüstungsständer] an Vinctilus gegeben]
20:26:34 cch [CHAT] 1 [Rüstungsständer] an Vinctilus gegeben

entityt tag: {NoGravity: 1b, HurtByTimestamp: 0, Attributes: [

{Base: 20.0d, Name: "generic.maxHealth"}

,

{Base: 0.0d, Name: "generic.knockbackResistance"}

,

{Base: 0.699999988079071d, Name: "generic.movementSpeed"}

,

{Base: 0.0d, Name: "generic.armor"}

,

{Base: 0.0d, Name: "generic.armorToughness"}

], Invulnerable: 0b, FallFlying: 0b, ShowArms: 0b, PortalCooldown: 0, AbsorptionAmount: 0.0f, FallDistance: 0.0f, DisabledSlots: 0, DeathTime: 0s, Pose:

{Head: [2.5344732f, 3.033558f, 0.0f], Body: [0.0f, 4.107684f, 0.0f]}

, Invisible: 0b, Motion: [0.0d, 0.0d, 0.0d], Small: 0b, UUIDLeast: -8582527041084213938L, Health: 20.0f, Air: 300s, OnGround: 0b, Dimension: 0, Rotation: [-90.0f, 0.0f], HandItems: [{}, {}], UUIDMost: -4325827720702114742L, Pos: [17.5d, 15.0d, 14.5d], Fire: -1s, ArmorItems: [{}, {}, {}, {}], NoBasePlate: 0b, HurtTime: 0s}

I'm sorry the I write garmen first XD
lg Vincent/Vinctilus