Inventory editors
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An inventory editor is a third-party program that allows adding or removing items from the inventory of a local character, and in many cases, edit other character data.
Inventory editors are primarily designed for the 
Desktop version of Terraria. It is strongly advised to back up the character files before proceeding to use any kind of inventory editor.
Terrasavr
Terrasavr is an inventory and character editor in a web-based app which includes a user-friendly interface. It is completely safe to use, since it does not interact with the files in the local Terraria directory in any way. Note that when saving a character file, it will have to be renamed to <name of choice>.plr to be used in-game.
This inventory editor can also be used on 
Mobile devices since the 1.3.0.7 update. The character files should be located in:
/sdcard/Android/data/com.and.games505.TerrariaPaid/Playersor/storage/emulated/0/Android/data/com.and.games505.TerrariaPaid/Players.
Browse > On My (device) > Terraria > Players.
One might want to use the editor in landscape mode on Mobile so that interface elements are not chopped up.
TManager
TManager is a free mobile Terraria hub app where users can explore and download world and players. TManager has recently introduced a full-featured inventory editor which supports editing character's details, inventory, Piggy Bank, Safe, Tools, Forge, Void, and Buffs.
Terraria InvEdit
Terraria InvEdit is a Windows-based inventory and character editor, designed to be compatible with Steam. The author appears to have abandoned it.[1]
The source code of the application was released to the public and can be used to update the editor to work with newer versions of Terraria, should someone wish to pick it up.
TR Save Editor
TR Save Editor is a free save editor for Terraria mobile that supports almost all character save data editing and some world save editing functions.
References
- ↑ [1.3.5.3] Terraria Inventory Editor (ABANDONED) Aug 29, 2018