/summon EntityHorse ~ ~-2.4 ~ {CustomName:"CHAIR",Type:0,Variant:7,Attributes:[{Name:generic.maxHealth,Base:1}],Invulnerable:1,Rotation:[180f,0f],NoAI:1,Silent:1,ActiveEffects:[{Id:14,Amplifier:1,Duration:199999980,ShowParticles:0b}]}

Explanation

This small command modification allows you to make chairs where you can sit on.

 ▶ [Activate the command just once] This command can look a bit messy and complicated but it isn't! Each part of this command gives to our horse some different attributes and I'm going to tell you why I used each one of them.

​In the first part ("summon EntityHorse ~ ~-1.4 ~") we are specifying that we want to summon a horse mob 1.4 blocks under the command block.

After specifying the type of the mob and the position where to spawn it, we are giving to it different attributes:

- 'CustomName:"Chair"' This bit of the command gives a custom name to the horse. You can avoid writing this part but you'll need it to make easier the process of removing the horses. Using this command '/kill @e[name=CHAIR]' you'll be able to kill all horses used to make chairs around the world.

- 'Type:0,Variant:7' specifies the type and variant of our horse. Because the type number is zero, we are summoning a normal horse instead a donkey or mule. There are different types of horses: black, white, with dots etc. but we are using the variant number 7 which makes the horse have no texture making him impossible to see.

- 'Name:generic.maxHealth,Base:1' This bit of the command makes the horse spawn with just 1 health point. We're doing this so when you "ride" the horse, you don't see its health bar texture.

​- 'Invulnerable:1,Rotation:[180f,0f],NoAI:1,Silent:1' With this three attributes we're making the horse invulnerable to surrounding hazards. We're also making it silent and "brainless" so he doesn't move. When a horse (or any mob) has not AI, it is not affected by gravity. By changing the rotation degree of a horse we can make it face in different directions. Use rotations of 90, 180, 270 and 360 (or 0) degrees.

​- 'ActiveEffects:[{Id:14,Amplifier:1,Duration:199999980,ShowParticles:0b}]' Finally with this bit of the command we are giving to the horse an invisibility effect. We already made it invisible but giving to it an invisibility effect, makes its name tag invisible. If the horse has the variant of 7 but no invisibility effect you can see its name while looking at it even if the body is invisible.

How to make working chairs