[Help] Keyframing time remapping makes me incapable of keyframing other effects

I didn't understand why keyframing sometimes wouldn't work. After googling the problem I realised that it wouldn't work, if you had already done time remapping keyframing. Is this working as intended? I am fairly new to PP, so I wouldn't know.

The only workaround I've found so far is nesting the time remapped footage into another sequence, but I'd love to be able to do it in the same sequence.

Here is a screenshot example: http://i.imgur.com/cmWojbM.jpg As you can clearly see in the screenshot, the linear wipe is supposed to be at 58 % (keyframe #1 is 100 % - completely black, and keyframe #2 is 0 %), which should make almost half the picture blacked out.

I'd love to get some help. Thanks in advance.