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That pretty much covers adding new hakpacks, of your own or others devising. The following topics cover some more advanced parts and how to edit hakpacks you or others have created.
Multiple Hakpacks
Once you start adding more than one hakpack you might get conflicts (see further down) but in any case most large hakpack projects have a load order - which you just need to follow using the "Move Up" and "Move Down" buttons on the panel.
The game loads them top to bottom, meaning the ones at the top are of a higher precedence, so our placeables.2da file in statue_torm.hak will be the one loaded by the game, while the cep_top_2_65.hak which also includes placeables.2da will be ignored so all the CEP placeable appearances will not be in the toolset or game.
Mainly 2da files will be overriden like this which needs attention, in which case you'll need to merge them by hand or manage data conflicts, then both sets of custom content will work together. Other conflicts like models and textures may be unavoidable (or actually wanted - such as your own models appearing over ones in other hakpacks).
Advanced: Removing Hakpacks
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