My best level yet, medium difficulty (I hope)
Haunted cathedral: 1DFA-0000-0044-837C

It has a few easy puzzles, a course that alters with the use of switches and a multi stage end battle. Since there are no checkpoints I made it so you can retry some of the sections and made it speed run friendly so you can run through the first part if you know what to expect. I tried to make it look nice in the zoomed out overview as well.
This took a lot more work than I thought, making it fool proof. Let me know if you get stuck anywhere.

Next I'll take a break from the editor, there are a lot of new course on here I want to try out :)

I'll try it tomorrow, sounds interesting.

I just played the ghost house level from gamexplain, try it out as well, it was fun.

I found one point where you can knock a spawning switch on a ledge and make an impassible corridor when you're big, updated it
New code: 1DFA-0000-0044-837C
Is that from AndreGX? Can you search on makers anywhere? Luckily he's in the top 5.

SMB3 - Trois - 00AE-0000-0044-95BB

I really like this level. I mean, it's a simple and random concoction of stuff, but I think it fits the theme of MArio Bros 3 very well. There's a lot of hidden stuff, and the end is kind of a sudden spike of "OMGWTF" in that I kinda threw everything at you, but it's not a hard level. Just simple and fun. Something I intend to do more often.

How do I add all you to my list of preferred 'makers'? Is that even possible?

That's correct, I made sure the trampoline and the fire were visible in the same screen as you went in and out of the pipe to hopefully make it obvious, and if that wasn't enough I even left a comment there basically telling you what to do. I guess I'll have to make sure my next level is easier to figure out... or not! :L

Also I'll play your levels tomorrow, they definitely sound like my type of courses!

Can we do action command jumps on enemies (pressing the jump button right when you land on them) to gain jump boost from them like SMB3? Or is it like Super Mario World/3D World where you had to be holding the jump before landing on them?

I find the latter difficult when needing to make tiny or medium jumps in 3D World. You can actually hold the jump button on SMB3 to do the jump boost as well but World and 3D Land/World didn't have both options :-/.

A few more levels I made~ I'm really enjoying making these then coming on here and seeing what everyone else has made~

7137-0000-0027-F876 (Stage Two-Still Awesomely Named)
69A4-0000-0040-52AE (Rail Run)
AB62-0000-0030-AE67 (So Many Paths)

my first musical level:
I tried to zelda lulaby and playing it also backwards for balad of goddess.
04C0-0000-0044-F012

My new level: The Spikes Have Eyes! And...it's underwater! I pretty much hate underwater levels, and SMM hasn't made that any better for me since most underwater levels in this game are garbage (at least the ones I run into while doing the 100-Mario Challenge), so I decided to make one that is neither cheap nor overwhelmingly basic. It's not incredibly challenging, but...it's a thing...so here you go. 

I'm making another level, and it wont really be easy. I am planning on deleting my latest level and replace it with my new one. That is especially since my latest level took almost no effort to make anyway. It was just a test to see if people liked that kind of thing (seems like they might not)