I found a lot of blogs and tried them, but they didn’t work. I wasted a lot of time, such as preference  & gt;   keymap   & gt; Main menu has many methods. Finally, we found a solution on stackoverflow

idea-community version 2021.1

macOS 10.14

Follow these steps:

Step1: shortcut key shift + shift (or CMD + Shift + a)

Step 2: enter vmoptions to see the idea.vmoptions file

Step3: edit file, add at the end:

-Dapple.laf.useScreenMenuBar=false

Step 4: restart idea