Update v3.3.0 - Added "gui-tool" option to config, this allows you to change the tool used to open the GUI from the default Knowledge Book to any other item. Renamed permission "commandgui.book" to "commandgui.tool", updated lang files, renamed command "/cg book" to "/cg tool".
Please add 'gui-tool: "KNOWLEDGE_BOOK"' to your config.yml or regenerate your config when updating.