The redstone category in the creative inventory includes various items which are directly capable of interacting with redstone (such as providing an output, or functioning based off of an input signal), and other items/blocks which interact with those. (some examples are armor stands, string, rail, and wool)

Missing from this category is the glass block, and slab block. While these blocks do not function directly with redstone, they are used commonly in redstone contraptions to control downward redstone signals.

Screenshots/Videos:

Example of a practical use of glass and slabs in redstone

Notes:

Related to MC-274141 MC-274142