This tool can be opened from the top bar RetroJRPG/Game Content

From this tool you can get an overview of important game content: Characters, Enemies, Abilities, Equipment and Items.
You can directly access any existing item by clicking on its name.
You can also create instances of these by clicking the “+” button.
Characters and enemies have a custom creation editor.
Creating a new Playable Character
Once you start creating your own game content. You might want to ignore the content included in the template.
In order to make the included content to stop showing up in the tool, tick ExcludeTemplateAssetsFromContent in the Project Settings/RetroJRPG
Press the update button in the Game Content window to refresh the list.