It appears you do not want to store linens so not really sure how to help , maybe pullout shelves pretty baskets.

You're on the right track with baskets. The idea is to be able to access collections without digging in deep, dark shelves.

Can't get more specific until you tell us exactly what you are trying to store or access.

Maybe drawer glide shelf additions, to help you easily access the depth of your closet? Like this ??? option 2 option 1

Pull out shelves that are usually seen for a kitchen pantry.

Pull-out drawer shelves, but you need a different door.

Pull out shelves /drawers, as mentioned. They can only be as wide as the available door opening width. The door would have to change as a start if you want to maximize the space.

You might be able to go to a local home improvement store, and get some off the shelf solutions that fit the available opening. Thats your easiest, and cheapest option, and worth looking into before going custom.

I have the exact closet. For starters I would turn the bifold into a single door. I just did it to mine today. I put brackets on the back and added a magnetic catch. Now it opens WIDE so it's easier to access the narrow space. Im buying a bunch of baskets to keep towards the front and stuff I rarely use will be stowed in back. Good luck.