1. Quantity or number (e.g., “two”)
2. Quality or opinion (e.g., “lovely”)
3. Size (e.g., “big”)
4. Age (e.g., “old”)
5. Shape (e.g., “round”)
6. Color (e.g., “red”)
7. Origin (e.g., “French”)
8. Material (e.g., “wooden”)
9. Purpose (e.g., “sleeping” in “sleeping bag”)
These exceptions tend to arise with stock phrases such as “hex nut” or “little black dress”. In that case the entire phrase, including adjectives, is treated as the noun, with additional adjectives prepended.
I would have thought that little black designer dress was correct. Designer little black dress feels incorrect. The L and BL in Little and black and then the Ds in designer and dress also lend an alliterative flow to “little black designer dress” that is not there for “designer little black dress”
https://en.m.wikipedia.org/wiki/Little_black_dress
So I think a little black designer dress would be a designer dress which happened to be little and black. A designer little black dress would be a dress of the “little black dress,” variety, which also has the trait “designer” applied.