Description:

This mod is a fork of RebelKeithy's Extended Armor Bars, which allows the armour bar to go above 20 points (stacking another coloured overlay on top of it), and adds an armour toughness bar to the GUI. This fork has two key differences:

The armour toughness bar is moved to the left side of the hotbar. I made this fork originally so that the toughness bar would not obscure resources in the Origins mod, but you may find this useful for other mods that need the space above the hunger bar.
The mod is available for all versions after and including 1.17+

To explain toughness if you are not familiar with the mechanic, toughness works as an additional damage reduction calculation applied to certain armour pieces when worn. Currently, only Diamond and Netherite armour offer toughness. You can read more about toughness on the relevant wiki page. Please take note that Toughness is a base-game mechanic, and this mod does not change or rework it in any way. It only allows visual armour stacking and an element to appear on the UI for visual feedback to the player.

As an obvious disclaimer, I do not claim credit for any of the content in this mod. All credit is reserved to RebelKeithy for the original mod, and tfarecnim for the toughness icon.

The mod(s) that add the cooldown bars in the screenshot are Origins, Origins: Classes, and more specifically, Expanded Classes: An Origins Addon.

[Fabric] Stacked Armour & Toughness Bars