You actually can't - or rather, of course you can, but it would be like "what do you want to do earlier this morning?" Grammatically sound, but rather nonsensical.
What you could say is e.g. "vad vill du göra nu på morgonen?" which would mean "what do you want to do this morning?"
Gotcha, so regardless of circumstance i morse, by itself, always refers to the current morning, dvs "earlier this morning," as in your comment above?
And if you wanted to say 'in the morning,' say... 'three years ago,' would it then be something like "...på morgonen tre år sedan?"