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From Minecraft Wiki
CustomDisplayTile: Optional. 1 or 0 (true/false) - whether to display the custom tile in this minecart.
[until 1.13] Optional. The ID of the custom block in the minecart.
[until 1.13] Optional. The Data value of the custom block in the minecart.
DisplayState:[upcoming 1.13] Optional. The custom block in the minecart.
Name: The name ID of the custom block.
Properties: Optional. The block states of the custom block, listed as key-value pairs under this tag.
DisplayOffset: Optional. The offset of the block displayed in the Minecart in pixels. Positive values move the block upwards, while negative values move it downwards. A value of 16 will move the block up by exactly one multiple of its height.