Learn English – Furniture as a general term for curtain accessories

What you have pointed to is a definition that explains how to understand a word when it is used in a certain way, but not when you can use the word in that way.

The term "furniture" has a well-known technical meaning in printing, for example. It means certain pieces that are fit among or around the pieces of movable type in an old-style printing press. But I think one would not use "furniture" to refer to other small accessories or fittings (such as a composing stick) that are used to assemble the type or operate the press.

If you search the Web for "rifle furniture," you may find a number of links to manufacturers or sellers advertising certain parts of rifles. (The word seems to correspond to the stock of a rifle or parts that serve the function of the stock.) A rifle has other accessory parts (such as sights) that appear not to be "furniture."

A Web search for "Mac furniture" is not as successful. That usage may have been intended to work by analogy, comparing the assignment of functions of graphical objects in software interface to the placement of pieces of furniture within a room.

So the question is whether "furniture" would correctly be understood when used to denote things such as curtain hooks. Unless you have observed multiple uses of the word in that way by people whose business it is to deal with such things as curtain hooks and rods, I would not advise taking the risk of using it that way. The risk of misunderstanding is large, since you mean to speak of things that are part of the general furnishings of a room but are not among the things most people would think of as furniture.