I guess I take a different approach - which may not apply totally to your situation. But here's what I do.
I don't generally buy a lot of furnishings and accessories in advance at random. (An exception is when there is a great bargain or I get a group of items all sold in one lot.) I usually buy or make pieces specifically for a certain spot in a particular room in a specific house. I do a lot of advance planning and decide before and as I am starting to build the house what the color scheme, wall, floor and window treatments will be, what furniture and accessories will be needed, and so on. I keep a list of each room on my computer and itemize all of the above. As I purchase or make or find or improvise each item, I strike through it on the list, so it can still be read but is obvious that it is already on hand. I can color hilite items to indicate if I intend to buy or make it. I also keep a box in which to collect the pieces for each room so I can find them easily.
I also make computer folders of photos I have researched online as inspiration and ideas for each room in each house: kitchen, bath, parlor, library, bedroom, etc.
What random and undesignated supplies I have stockpiled, I keep stored in boxes arranged by type: wallpapers in one, fabrics in another, little odds and ends of findings that might come in handy in another. I keep scraps and left-over pieces of paper and fabric in folders, labeled by the room in which they were used.
I use plastic silverware trays to sort and organize similar sizes and shapes of long wood dowels and "boards" and deeper plastic bins for larger and odd shaped wood.
As I finish a house, my boxes of furnishings are emptied into the rooms and I can see at a glance where everything is. I may still have a few things in reserve, but everything has its place.
I don't keep a large inventory on hand for three reasons: 1. I don't have a lot of space to store stuff. 2. I am cheap frugal and don't want to spend a lot on stuff unless/until I need it. 3. It is easier to keep track of stuff if you don't have a huge amount of it around.
So that is my tuppence worth.