Most likely, Unit Manager is from Universal Tower Defense X on Roblox, since a recent guide shows the Unit Manager is opened there by selecting a unit and pressing G.

Why this seems likely

The clearest match I found is a June 2026 guide for Universal Tower Defense X that specifically explains how to open the unit manager and use it to sell units, toggle effects, enable auto-upgrade, and manage abilities. Another source for the broader Universal Tower Defense series describes the game as one where you collect units through a summon system and use them in battle, which fits the “unit manager” style of gameplay.

Possible confusion

There is also a Unit Manager page for Garden Tower Defense , but that refers to a UI element for placed units rather than what most players mean when they ask which game “made” Unit Manager. So if you saw the term in a Roblox TD context, Universal Tower Defense X is the best answer from the sources I found.

Quick scoop

Answer: Universal Tower Defense X.