The startup item can only be added when the list menu is selected, and the next menu can only be added when the directory menu is selected.
To add music file startup, the first thing to do is to create a list menu:
Long press the left button on the icon button, and the modification will appear. Click to enter the edit menu, as shown above. Select the icon name and menu type, and then click OK.
Then open the created new menu. Usually, there will be a default project named Unknown. If you press it for a long time, there will be four buttons for editing: Add, Move and Remove. After selecting Edit, the interface as shown in the figure will appear.
Here you can set the project start. You can see that if you want to add music, you can choose the second file option. Then select the location of the music file you want to create.