I run 4th Edition D&D and I've not come across anything like that, although I haven't been running things on Roll20 long. I normally end up writing up one or two new monsters for each session, whether I will be using them or not, and it fairly quickly builds up a selection of monsters to choose from. I've found I don't need to fill in a character sheet for a monster, just add the main stats to the Attributes and a few macros for the attacks etc in the Abilities list. Any special abilities such as resistances, and any equipment they might be carrying goes in the GM Notes in the Bio and Info section and also in the Token's GM notes for quick reference. If you run multiple games you can use the vault to transfer monsters from one game to another to save you having to write them up more than once. You might also want to consider creating a 'Holding Area' game to store all the monsters in once you start to build up a collection, it means you can just transfer over the ones you want for the current part of your game ahead of time instead of having to search through hundreds of monsters for the right one when actually running the game.
