So... why does the asset manager not have all the assets in it?

[Elfe]

You need to setup your additional browse / source directories correctly to make it work.
I’ve written a tutorial about how to do this here:

[Script][Basics]Modding Beginner's Guide I

Summary: This tutorial scopes with the setup and a basic overview of the most relevant modding tools. It therefore shows how to setup the Asset Manager properly and a further part explains how to create your first mod. Parts Index Modding Beginner’s Guide I Modding Beginner’s Guide II Modding Beginner’s Guide III (yet to come) Index 1.0 Preparation 1.1 Tools Overview 1.1.1 Asset Manager 1.1.2 World Editor 1.1.3 Quest Editor 1.1.4 Conversation Editor 1.1.5 PSEditor 1.2 Prepar…