Sadly, there is no way to make a custom conveyor belt in SMBX as far as I am aware of. However, as it was already mentioned, there are SMB3 conveyors in the NPC tab. It's possible that you could re-texture the conveyor belt as the same frame for each, but it would be slow. There is also no way to change the speed of the conveyor.
55jedat555 wrote:I hope that sometimes in the future a thing like this could be made with SMBX.
I'm sure many users would enjoy that too. If it were implemented, it would not be by redigit, but probably with an external program or coding.
This isn't related to issue, but "Kumikyoku Nico Nico Douga" (The video) is awesome!

I'd love to re-create that in SMBX, but that probably isn't possible right now due to not having the option to create custom-made conveyors.