The new modern model-driven app designer has an easy to use interface, and in sync with canvas app designer. However, the preview has the following known limitations.

• You can’t add the following model-driven app components:
  • URLs
  • Business process flows
  • Charts
• You can’t add more than one area to the app’s navigation site map.
• You can’t change the app’s icon.
• You can’t specify the app’s URL.

You can use the Switch to classic option to use the classic designer to complete the above app design tasks.

Don’t be like our Buddy in the above comic strip, always check the official docs to see the known limitations, read more here.

• I Wish I Would Have Known