KleeSlabs

KleeSlabs is a mod created by BlaytheNinth based off of a suggestion from Kleetho. It allows the player to only break the one slab being pointed at when two slabs are stacked on top of one another. It allows for configuration of this functionality to allow for greater control of the breaking mechanic of stacked slabs.

With the "Require Sneaking" configuration option enabled, a single slab will only be broken when the player is sneaking while breaking the block; otherwise, both slabs will be broken as per default vanilla mechanics. With that option enabled and the "Invert Sneaking Check" option enabled, single slabs will be broken by default and can be suppressed (to use the default mechanic) by sneaking.

Mod compatibility
The slabs it supports is not universal. Its currently supported mod slabs are as follows.
 * Quark
 * Botania
 * Biomes O' Plenty
 * Forestry
 * Extra Trees
 * Applied Energistics 2 (1.7.10 only)
 * Thaumcraft 4 (1.7.10 only)
 * Thaumic Tinkerer (1.7.10 only)
 * Witchery (1.7.10 only)
 * The Betweenlands
 * Underground Biomes
 * Missing Pieces

Some mods have no intention for compatibility due to technical reasons. Currently, this has only been explicitly stated as such for Immersive Engineering, because its slabs are not normal blocks but also create tile entities.