Shadow new

Im still trying to figure this out. I do use bartender and i understand the switch action bars. What im trying to figure out is what macro goes where. It looks like im seeing in the posts a bunch of different macros as shown below.

/targetenemy [noharm]
/cast [noform] !Shadowform
/castsequence [combat] reset=0.5 0,1,2,Shadow Word: Death
/castsequence [combat] reset=0.5 0,1,Halo
/castsequence [combat] reset=0.5 0,Shadowfiend
/castsequence [nochanneling] reset=target/19 Shadow Word: Pain,Vampiric Touch,Mind Flay,Mind Flay,Mind Flay
/castsequence Mind Blast,Mind Blast,Mind Blast,Devouring Plague
/use 13

I understand the whole 0,1,2 are equipment slots so im taking those out for now unless you have to use them. The last lin is alos your trinket whereas im not using that atm until i get a one with a use lol. So are the first 3 lines macro one, then the next 2 lines macro 2 and the last two lines macro 3. Or are there in fact 5 macros to mess with. Just curious how this one is set up. Been trying everything and it keeps getting stuck or just casting swp.

read https://wowlazymacros.com/forums/topic/the-castsequence-reset0-3-0-explanation

Ok ive been testing this one out. It works great cept i would like it to hit Devouring Plague when it procs. It doesnt cast and sometimes lets 3 or 4 other casts go thru first.

/targetenemy [noharm][dead] 
/castsequence  [nochanneling]  reset=combat Shadow Word: Pain,Vampiric Touch,Mind Flay,Mind Flay,Mind Flay
/castsequence reset=combat Mind Blast,Mind Blast,Mind Blast,Devouring Plague
/cast halo

Here is my take on the shadow macro, dissect and make changes so i can get better. I changed the devouring plague because i found at 20% shadow word death was procing a shadow orb and often more than not mind blast procs twice before DP came up in sequence.

/targetenemy [noharm]
/cast [noform] !Shadowform
/castsequence [combat] reset=0.5 0,1,2,Shadow Word: Death
/castsequence [combat] reset=0.5 0,1,divine star
/castsequence [combat] reset=0.5 0,mind blast
/castsequence [nochanneling] reset=target/18 Shadow Word: Pain,Vampiric Touch,devouring plague,mind flay,mind flay
/cast Shadowfiend
/use 13