Yes, but it is part of the CoreGui and since it is part of the CoreGui you will have to change a lot of stuff as you can’t access the CoreGui (in which the original code migh access)
Don’t reference from Roblox’s CoreScripts repository. It is heavily outdated by several months or years. The latest copy of the CoreScripts can be found either through CloneTrooper1019’s Client Tracker (which automatically receives and unpacks updates) or your local filesystem.
What I do to make a custom backpack system is this:
I disable the CoreGUI Backpack module which disables the default backpack system.
From there you can use the principals that if a tool is parented to the players character, it is equipped, or if parented to the players backpack, it’s unequipped.
A simple tool.Parent = player.Character will equip the tool. From here you can create a custom GUI to go along with your system.