5E customizing Monster Manual / compendium NPC stats

Hey folks, So I've been making some changes to some of the out-of-the-box NPC stats for monsters from the compendium in my 5E game, mostly buffing them up or adding abilities as my players progress. I've mostly been able to do what I want, but some things seem a little wonky, and I'm not sure where I should be making changes. So there's the option to change things in the "character sheet" tab by clicking the gear icon. Then there's the option to change things in the "attributes and abilities" tab. I don't understand why changing things in one or the other place seems to work better in some cases? like some things seem to need to be changed on the character sheet and some on the A&A page. I also don't quite understand how all the fields in the A&A page map to the various abilities (are the only applicable fields for NPCs the fields that start with NPC? for example). So my questions are -- do best practices exist for this? a guide? I'd like the changes to persist into future iterations of the NPC. Which of the possible change areas -- character sheet or A&A tab -- is the best place to change those values, so the changes affect all the related abilities? Is there a guide to understanding the fields in the A&A tab? thanks for the help!

In general, if you are changing what is entered in a field, it is best to do it through the character sheet. The A&A tab is what is left over from the original implementation of Roll20, before character sheets were added. Character sheets gave us things like repeating fields (inventory, traits, attack, etc.) that the A&A tab lacks. Nowadays the A&A tab is best used for introducing whole new fields, such as if you want characters to have an Agility score for example, or to correct some things that are not shown on the character sheet, such as some of the fields that are used to flag a status for the Characetrmancer: "under the hood" modifications. My advice is to make modifications on the sheet tab for things like adding new attacks or abilities or modifying the value in a field. Use the A&A tab only if you want to make additions of things that are just not in the context of the existing character sheet, such as if you need to track a brand new field, like "Reputation", or "Patron deity". TL;DR: Use the character sheet for modification if at all possible, and resort to the A&A only for truly novel changes.

Best practices: If you are using a character sheet, completely ignore the attributes & abilities tab. Do not attempt to adjust attributes via that at all. The A&A tab is useful for people who are playing without a character sheet, but it's a legacy feature that you should regard as obsolete if using a character sheet (and can sometimes - very rarely - cause issues with attributes). Edit: I agree completely with keith, especially his TLDR: Use the character sheet for modification if at all possible, and resort to the A&A only for truly novel changes.

Awesome -- thanks to you both; that makes sense. So I think I can go forward with that, but the one thing I may have overlooked in the character sheet (D&D 5e NPC by roll20 sheet) is where to change an NPC's proficiency bonus? and if I change their strength, for example, in the character sheet, the change should affect any strength based rolls listed under their actions? thank you!

The bonuses in attacks for NPCs is deliberately divorced from mechanics. The designers of the game mostly followed rules when determining those, but not always. Likewise, Ability rolls are modified by the Ability value if nothing specific is entered, but if the creature has "proficiency" in a skill, this is input manually and acts as an override. PC sheets largely follow the rules mechanically. NPCs are mostly manual, to account for designer overrides.

Ah-ha, great -- makes sense. So I should change abilities and expect that those changes would affect saves and abilities, but change attacks specifically to update attacks. what about spells? are those manual as well? or hooked to the ability? thank you!

Use the create a character api to speed up the process.  We are talking seconds, but that could be minutes into hours depending on how many monsters/npcs you manual add.

not sure what you're referring to,Muckbuckle?

Ken R. said: Ah-ha, great -- makes sense. So I should change abilities and expect that those changes would affect saves and abilities, but change attacks specifically to update attacks. what about spells? are those manual as well? or hooked to the ability? thank you! Spells should be hooked to the ability, but there are fields on the NPC editing screen (the one you get when you click the gear icon in the upper right) for setting caster level and save DC.

ah, okay, I know what caster level means, but how does R20 translate and apply it? thanks!