I use Ulysses to organize most of my D&D stuff; here’s the basic Markdown template I use for monsters (some additional items can be added for more advanced monsters, such as those with special abilities and spells).
# NAME
*SIZE type, alignment*
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**Armour Class**
**Hit Points**
**Speed**
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**Str** | **Dex** | **Con** | **Int** | **Wis** | **Cha**
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**Damage immunities**
**Condition Immunities**
**Senses** passive Perception X
**Languages**
**Challenge** X (XX XP)
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**Actions**
***Melee*** *Melee Weapon Attack*: +X to hit, reach X ft., X creature. *Hit*: X (XdX+X), X-type damage. (Effects)
***Range***: *Ranged Weapon Attack*: +X to hit, reach X ft., X creature. *Hit*: X (XdX+X), X-type damage.
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**Equipment**
Excited Pixels 