I went to make a homebrew monster, a variation of the Xorn, since I was on that wiki page which i will link here: https://forgottenrealms.fandom.com/wiki/Xorn
so anyhow, i hit create monster, started with the xorn as a base, was gonna make the Xaren, a version of the xorn but with like metal skin and more dangerous. I've made a lot of homebrew creatures, but I've never had this show up. when i look at the creature stat block (not that i had changed anything at the time of the screenshot) it was all normal. 

I thought perhaps it had some interactivity in the encounter maker, so i go check it there and... it doesn't! why is there so much coding stuff here? I've had to do some for homebrew races and sub-classes I've made and gosh its so archaic feeling, but other than denoting skills and conditions i haven't had to do much in a monster stat-block. What is this stuff? What's it for?

They are starting to implement the underlying code to make things rollable directly on monster statblocks. (For: DM’s, Wildshape, Animal Companions, Steal Defenders, Summoned Monsters, etc.) You are seeing the code for what will be coming in the very near future.

Some of that coding dictates that it’s rollable, some governs what it looks like, some governs what it actually does, and it looks like the last part is dictating what it will show in the campaign log I think.

ah ok. so i take it this feature isnt quite finished yet?

If it were, we could roll from the statblocks already.