You can find the full list of permissions as well as their default states in the wikiĭeveloping a plugin like this requires a lot of time. Players need the 'e' permission in order to be able to use the plugin!

backpack.noCooldown - Allows to bypass the cooldown to open the backpack.backpack.keepOnDeath - Allows the player to keep their items in their backpack on death.- Allows the player to edit backpacks of other players.backpack.others - Allows the player open backpacks of other players.- Allows the player to clean other players backpacks.backpack.clean - Allows the player to clean their own backpack.backpack.size.1 - Mini size for a backpack, if the player has e permission he will also have at least a backpack with the size 1.backpack.fullpickup - Allows the player to automatically pick up items when their inventory is full (function needs to be enabled in the config).Please use the 'backpack' permission in cause this permission is not working for you. Some permission plugins have problems with this permission. e - Allows a player to open their backpack.If you are still using Java 7 you can use this version. (Optional) PCGF PluginLib ( Advantages of using the PCGF PluginLib).

Bukkit, Spigot, Paper or Uranium for Minecraft 1.7.10 or newer.Preserves the NBT data of items (everything that can be stored in a chest can be stored in the backpack).Item filter (block items from being stored in the backpack).Multi language support ( multiple language file included).Multiple storage back-ends (Files, SQLite, MySQL).Shortcut item to allow faster interaction with backpack (can be disabled in the config).Auto item-collect on full inventory (can be enabled in the config).Backpack size controlled by permissions.Minepacks is a free and reliable backpack plugin with different backpack sizes, fully customizable language files and MySQL storage support.

Minecraft mods backpack 1.12.2