You have two choices
ONE!
All deserts that aren't baked go in deserts. All things that are baked go in baking.
TWO!
All deserts go in deserts, and everything else that is baked goes into baking.

THE CHOICE IS YOURS!

or

THREE!
Since it's blank, do whatever you want.

I would think it odd to see an apple pie or a chocolate cake in the baking section when there's already a desert section, so I would put all deserts in the desert section, and save the baking section for breads. You could even change the name from Baking to Breads or something else to lessen the confusion.

If the divided name sections can't be changed, I would go with all desserts in Dessert, and breads and breadstuff in Baked. But that's just me.

Yeah, the tab names cannot be changed. I don't bake lots of breads or breadstuffs... I guess I have to start now, huh? :)

I'd put the casseroles in the main course/entree section.

That categorization is a bit odd.

I agree with iconomy. In baking, I'd put biscuits, cornbread, rolls, bread, breadsticks, etc. I might also add muffins, popovers, and tea breads. I'd make the judgement based on this question: at what part of the meal would I eat this baked item? If it's during the main body of the meal, or before, I'd put it in baking. If it's after the meal as a sweet, it would be dessert.

Some people do refer to their cookie and cake making as 'baking,' but I don't hold with them.

There's a strong association with the word "baking" referring to breadstuffs, so even though lots of other food is certainly baked, that wouldn't lead me to call making a mac and cheese or chicken pot pie or roasted veg "baking." They're main dishes or sides.

I can't stand the way recipe cards and books are set up - it's precisely this kind of thing that drives me nutty. In addition to my cookbook collection, I just keep a spiral bound blank book and write recipes in as I adopt them, willy-nilly. I saved a few pages at the front for a Table of Contents, so when I add a new recipe, I just write a new line in the ToC and number the page. In a way this is really nice because it's almost a journal -- each recipe was added at a specific time in my life, and if I can't remember which page it's on, I can usually remember about when I started cooking it, and open the book to roughly the right neighborhood for the recipe I'm after. I also have fun making little illustrations in the margins or writing little tales about who gave me the recipe or how I discovered the food.

When I encounter a new recipe that I want to try, I usually tear it out of the mag/print it off the net and stick it in the cover of the blank book. When I get around to actually making it, I only enter it into the book if I think it's something I'd want to make again. If not, I throw it away. There's a constant backlog, but that's kind of fun.

You could also maybe just cut the "baking" tab out (if you don't make a lot of breads) and let the pages supplement the previous section.

There's a strong association with the word "baking" referring to breadstuffs, so even though lots of other food is certainly baked, that wouldn't lead me to call making a mac and cheese or chicken pot pie or roasted veg "baking." They're main dishes or sides.

Agreed. In fact, all my big cookbooks, vintage and modern, baking is breads or rolls of some kind.

Where did you get this new recipe book? I've been wanting one, but the lack of choices here are making me lean toward a plain notebook.

Sweets in desserts savories in baking.