Why the Constitution grants the president the power only to pass or veto a whole bill and not just parts of it?

Explanation:

I don't know much about constitutional law, but I think your suggestion would create chaos). Think what might happen if the President had 4 bills on his desk and all had parts that had to be revised to satisfy him.  Remember that the Senate and the House have already given their approval.

Now these 4 bills go back for debate, or clarification, or whatever else the President doesn't like and the whole process starts all over again.

I'm trying to say that nothing would ever get done.

i think it’s a i hope that right : )