Enter Responsive Design Mode Shortcut doesn't work
Solution 1:
The shortcut in Safari for Responsive Design Mode is controlcommandR (not shift).
To activate this mode, you'll also need to make sure you have enabled the Develop menu. If you haven't, you can activate it by clicking on the Safari menu in the menu bar, then clicking Preferences, and under the Advanced tab enabling "Show Develop menu in menu bar."
Once the Develop menu is enabled, you'll see the Responsive Design Mode toggle (along with its associated keyboard shortcut) under the Develop menu in the menu bar, as pictured below:
