So I'm new on D&D Beyond, I've tried searching around for how to utilize Commands for Reactions, saving throws, etc. I'm inserting an Unearthed Arcana Monk Subclass Playtest Material as Homebrew (Public) for everyone to use. However, I'm having trouble as to how I go about doing so. Can anybody pass me a general List of BB Codes that are specific to D&D Beyond I can properly make this (Sub)Class on here?

First of all, you can't publish UA homebrew. It is against the rules.

Second, are you refering to snippet code? https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/25930-using-snippet-codes-in-your-homebrew

More or less the Snippet Codes, but trying to modify them to make them usable for the Monk Class/Subclass. Also, the UA thing I did not know. I'm just trying to convert it from the PDF File to use in a Campaign I'm in v.v (how do I make it Private again)?

Quote from KerubinSigma >>

More or less the Snippet Codes, but trying to modify them to make them usable for the Monk Class/Subclass. Also, the UA thing I did not know. I'm just trying to convert it from the PDF File to use in a Campaign I'm in v.v (how do I make it Private again)?

 
Snippet Codes are here. (Clicky)

Homebrew you make are automatically private and are automatically shared between everyone in your campaign. 

Okay that works, thanks ^.^

Also, the way of the astral self has been added to DDB (if that is the UA monk subclass you were refering to).

Quote from KerubinSigma >>

I'm inserting an Unearthed Arcana Monk Subclass Playtest Material as Homebrew (Public) for everyone to use. 

 You are not allowed to publish anything as public homebrew that isn't your own creation. This includes UA, other peoples homebrew and third party content (such as DMs Guild)