There is a new issue in Super Mario Maker 2 that allows players to incorporate all elements into all types of Mario courses, including elements exclusive to Super Mario 3D World.
Mario Maker 2 is a game that allows players to create their own Mario courses. Players are given many tools to create their own Mario levels. Most of the items and enemies from the Mario games are available, and players can choose themed routes based on the different aesthetics of the Mario games. For example, players can create a course in the same style as Super Mario World or Super Mario Bros. 3.
Some articles are exclusive to certain Mario thematic courses. For example, clear pipes can only exist in 3D World course. However, there is a new issue that allows players to use all items on all types of courses.
How to use 3D world objects in all game variations
The video below shows in detail how to accomplish this little problem. There is a Kotaku article which also explains how the glitch works.
Related, related, related: Super Mario Maker 2 review
The first thing to do is to create a new stage. Place a block of questions on the screen, then place a track on the block. Attach a part to the track and delete the track. Removing the track forces the room and question block to exist in the same location, although this should be impossible in the game.
After that you need to place any item on the screen; that newly placed item will then be pinned to the rightmost item bar on the screen. Save this course and try to load it again. The game will recognize the course as corrupt and delete it.
The next step is that you have to do a new course several times until you start in 3D World themed courses. The item that is pinned to the top right taskbar still needs to be saved, and players can place that pinned item on their new 3D World course. But the pinned item has become a "converted item" and it will be invisible in the course.
You then repeat the previous process, ask a block of questions, and then place a lead on the block. Attach a part to the track, delete it, then place an object on the screen. Rather than defining an item, place an exclusive 3D World item. The item is pinned in the upper right corner and becomes a "converted item". You can place it in any other Mario-themed universe. It will be invisible, but it will have the same properties.
The video shows what the different objects will look like invisible, including clear pipes and boots. The video is from SilicatYT - Glitch Tutorials' Youtube Channel.