I use a mod that lets you set a predefined inventory upon world startup. The thing is... I use mods in one version that aren't in another, and most of these mods don't have versions released for the other. And the mod uses the config file to save the inventory set, but the problem is the mod uses the same config for all versions. Is there some way to add a config file for both versions separately? It's not crashing, it just doesn't load any items in one version (not even vanilla).
If you play multiple versions of Minecraft with different mods I recommend using MultiMC.
MultiMC is a free, open source launcher for Minecraft. It allows you to have multiple, cleanly separated instances of Minecraft (each with their own mods, texture packs, saves, etc) and helps you manage them and their associated options with a simple and powerful interface.
For your particular setup you'll only need to:
- Install MultiMC
- Create two instances of the Minecraft versions that you use
- Move the relevant mod files from your current installation to the relevant instances, or add them via the 'Loader Mods' tab in the 'Edit Instance' window (recommended).
See also getting started.
This will work for most cases, the only time it won't work - as far as I know - is when the mod author has hard coded a path to a config file to somewhere outside of the instance folder, which they really shouldn't do regardless.