Well if you want the worst in the genre I'd recommend Fashion King lol

For something fashion adjacent, I enjoyed Miss Korea

I don't recollect seeing many dramas with this set up.
Recently, Record of Youth felt like it tackled this subject quite well (until i dropped somewhere at ep 10).
Baby faced beauty? It's an old drama. So I don't remember much. But i think she worked in the fashion industry.

Model starring Kim Nam-joo and Jang Dong-gun. A classic.

Now we are breaking up has a fashion designer and photographer as the leads. If you don’t mind annoying ex fiancées and vicious mother in laws, side character affairs, noble idiocy and spoilt heirs then this is likely to have enough of the fashion world to meet your needs. You see the cut throat nature of lines being copied for the knockoff market, the fight to stay prominent in the department stores and the competitive nature of the international and domestic lines.

The first that comes to mind is Glass Mask. Really good. And the first time I got an in-depth concept of the technique - cross-stitching.

Others are...
VIP
Kill Heel. I'm really reluctant to name this one since it became a collosal mess for me.

I Do, I Do The FL is a shoes designer and had a great room just for her own shoes :p

Cheongdamdong Alice I don't recall so much... I think I wasn't a fan of the FL

The Royal Tailor It's a movie but I really liked the part about tailoring.

She Was Pretty is set at a fashion magazine.

Jang Bori Is Here for hanbok fashion

For someone who is a bit into fashion, I dont have any names in my head that the leads work in this field. Wow.. I unconsciously managed to avoid all the above-mentioned fashion dramas. So strange.

Though it’s far from perfect, Laurel Tree Tailors has its moments….particularly the runway scene featuring the four male leads: Lee Dong-Gun, Cha In-Pyo, Choi Won-Young, and Hyun Woo. Loved watching them strut their stuff!

I think it would have to be Baby Faced Beauty - I watched it so long ago that I barely remember anything, but I DO remember the arc at the end where the heroine is designing a dress while temporarily colour blind. That was some good TV, and it's stuck with me.

There are several Chinese dramas I’ve liked that are fashion based. They all have a similar storyline-girl trying to break in, man is CEO in industry, they clash and eventually help each other out and fall in love. There’s often some older craftsman that they have to save or convince to help them. The business is always cutthroat and about winning China international renown. I like them when I really don’t want to think. (They are also all better than the most recent Kdrama fashion drama that should not be named.)
Love Designer
Sunshine of My Life
Are the ones I could remember for now

Besides She Was Pretty and Fashion King, I have nothing substantial. It came to mind though that some of the older dramas had characters who had a fashion connection. Full House's second FL is a fashion designer. Goong's FL is a fashion major.

"Kill Heel" was about a home shopping channel but had fashion mixed in since they sold clothes. The storyline was kind of makjang but I loved Lee Hye-Young in it. She was also in "Mother," the Korean remake, and I think she plays memorable characters. I also enjoyed Kim Sung-Ryung's performance in "Kill Heel."

Perfume with Go Won-hee and Shin Sung-rok! I loved the designs and Shin Sung-rok's character is one of those few characters who embodies the designer character philosophically not just artistically (on a side note, Shin Sung-rok was just made for the perfectionist Yi-do who, in spite of his theatrics, was a decent human being). Also, I loved how the drama developed the leads' relationship in a slow and warm way.

Ah, I just remembered. Lee El in 'Matrimonial Chaos' was a bespoke fashion designer (seamstress?), owned a shop. The oddest part of the otherwise excellent series was Lee El's clothes were so oddly voluminous and ultra-concealing, sometimes resembling nun's habits.