Yes it is possible using a trick.
First go to General Behavior tab in Settings and make sure "Expand folder shortcuts" setting is checked. Then follow these steps:
1. Right click the folder you want to add as expanding menu and click Copy.
2. Open the folder: %AppData%\Microsoft\Windows\Start Menu and right click an empty area and click "Paste shortcut" (or use the Paste shortcut command on the Classic Explorer toolbar).
3. This creates a special symbolic link shortcut to the folder. It works only for %AppData%\Microsoft\Windows\Start Menu meaning this link can only be created if the shortcut is pasted in the Start Menu folder.
4. However, once this link is created, now you can cut this shortcut and paste it anywhere inside any folder in the Start Menu. It will expand as a cascading menu.