recently I just fight for the same issue for one days. Maybe there is the same root cause for your problem. Below is my root cause and solution:

The Cause:

I add some defination of my data in the namespace before the defination of Form1. After I did this, the submenu "View Designer" dispeared. show as below: enter image description here

The solution:

Move the user defined class at the back of the Form1 defination.

Hope this is helpful.