I have an "L" shaped desk in my sewing room also. Start with the big things. Where will each machine be located? Which supplies are needed in every operation of 1 machine? I have all embroidery machine tools, accessories, and thread located in drawers directly below the embroidery machine. All domestic sewing machine tools, and accessories are located in a drawer right below the machine they go to. All cotton thread is in one drawer along with quilting needles and other quilting supplies. Other spool threads and needles are in another drawer. Serger cone thread is in a drawer closes to the serger, along with those tools and accessories.
Now move to your cutting area. All cutting tools are located in this area - rulers, rotaries, large scissors, templates.
All fabric is stored in one area, a section for yardage, another for FQs, another for strips. My fabric storage is the closet.
This arrangement works for me in a 10x12 second bedroom. I arranged/re-arranged quite a few times before I got it the way it works. Of course if I add anything I have to move things again. That's OK - it makes me clean things out. I have to keep things where they are used, or they would never get put away. Oh, my computer is in a custom cabinet (I made it) behind my sewing desk, and dh also has a craft table in this room! I have a big enough wall exposed for a 4x8 design wall, my TV is mounted where I can watch it while I sew, and the ironing board is only out during piecing.
Good luck finding what works for you.