It’s a right+click on the parent column to bring up the option to “hide this”. As far as your modes troubles, it may have to do with your source footage. Do you have at least 2 layers that can interact with each other? Not all footage will react with every mode due to differences in chroma and luma. Try this: creat a new layer and apply Render>Ramp to it. Make the ramp colors something gross like a pink and bright green. Make sure this layer is a the very top of your comp. Now monkey with the modes and you should get _some_ sort of reaction/color change. Since you’re new to AE here’s a really cool way to hammer through the transfer modes to find the coolest one for each unique situation. Select a layer, hold shift and hit the + and – keys on your keyboard (not the extended keyboard). Great for lots of choices quickly.
Good luck and welcome to AE. It’s really a lot of fun.
Scott