3. Add a second rail under the shirts
If step one found 20 inches of air under your hems, this is where you claim it. A second rail across the short-garment half of the closet roughly doubles that section’s capacity.
The simplest version is a hanging double rod: a frame that hooks over the existing rail and drops a second bar 25 to 30 inches below it. They cost around $15, CA$22 or £12, need no tools, and come out when you move. Check the drop length against your hem measurement plus two inches of clearance, and check the hook width fits your rail diameter.
The sturdier version is a fixed rail on brackets screwed into the side walls. In a plasterboard closet use proper cavity anchors rated for at least 30 lb each, and set brackets no more than 36 inches apart or the rail will bow under a winter’s worth of coats. A wood-backed closet is easier — screw into the timber and forget it.
Split the closet logically: one full-height section for coats and dresses, one double-rail section for shirts above and trousers or skirts below. Put the things you wear weekly on the upper rail at natural reach height, and seasonal or occasional items on the lower one, since bending is the cost you pay least often.
If the closet is shared, give each person a vertical block rather than a horizontal one. Splitting by upper and lower rail across the full width means the shorter person spends every morning on tiptoe.