Can the Black and Decker toaster oven, model TRO55, be used for baking?
Did you just buy this model and do you still have the receipt? If so, I'd return it, explaining that while it says you can bake in it, that it's not possible since it's not possible to turn off the top broiler element. Attempting to bake in it will only burn the top of your food. Explain you'd like to get another Black &amp; Decker model - TRO2000 which does allow the selection of just the bottom element for baking. 

On the other hand, if you've had this model for a while but never tried baking in it before, I highly doubt you'd be able to return it despite what I consider false advertising (since every site where I checked the model said it could bake - yeah, right)!

What I suggest is to experiment a little to see if it's possible to bake certain foods in it. No matter what you do, I'm sure that baking anything that rises high (such as breads, popovers or 'angel food' type cakes) won't be possible without the top being burnt by the time the rest is baked.

Next time you make a pan cake, choose a pan that will fit in the oven but with higher sides than normal. Since your model has a convection option, turn that on too. With the convection feature plus heating from both the top and bottom, keep an eye on your cake as it's quite likely to bake in less time than a conventional oven. I've never used one so I'm speaking from common sense rather than experience. When the cake has risen enough and the top looks properly browned, test the cake's doneness using a wooden toothpick or skewer inserting into the centre. If it still needs further cooking, loosely cover the top with aluminum foil to prevent over-browning.

I'd suggest keeping a pad handy and noting how long it took to brown, when you covered it with foil (if you had too) and when it was finished baking. That way, you'll know what to do next time. If it works for a pan cake, it may also work for cupcakes. If you need to cover them with foil if browning too fast, the tops should be sufficiently cooked so the foil won't stick. That's why I suggest a pan with higher sides.

It may be possible to bake foods like cookies and biscuits with no problem since they cook quickly. Always use the convection setting when baking so heat distributes faster and more evenly. For all baking, experimental or otherwise, use the lowest shelf possible. 

If I'm right, you can select a temperature for your oven - the broil feature doesn't stay on the whole time but cycles on and off to maintain the temperature chosen. With your first baking experiment, set the oven 5-10 degrees (Celsius) lower as a test. If you're concerned about over-browning, it would mean the broiler element would be on a little less. 

These are only suggestions and you'll need to test them yourself. If I had the model you have and really wanted to bake in it, it's what I'd do. Despite everything you try, it's possible you can't really cook any baked flour goods in it other than cookies. But give it a try if you can't return it.