Hey thanks for your comment!
The expansions all go in /GuyEngine V2/Expansions/
An easy way to find it is to just open the plugin, navigate to the preset browser, and then in the top right corner, click "more" and then "show preset folder" and that'll open the /GuyEngine V2/ folder I mentioned above. You should see a folder for expansions. Inside that folder, you'll place all of the subfolders that start with "000"
So GuyPalette would be installed like /GuyEngine V2/Expansions/0006 GuyPalette/
Remember that all of the "000" folders that are included must be also in the expansions folder due to the plugin's indexing system. I hope that helps! Let me know!