Sub Menu items changes to the Parent Menu Items in the Secondary Menu

[RohanSharma2598]

Description

When we create a Menu in Appearance > Menus in a way that it has Menu Items and sub-items, and then go to Appearance > Customize > Header, add a Secondary Menu block, and select the Menu which has Menu items and sub Menu items, it changes the sub-menu items to the Main Menu items.

Step-by-step reproduction instructions

1. Go to Appearance Menus and create a Menu with items and sub-menu items.
2. Set it as Secondary Menu and save the changes.
3. Go to Appearance > Customize > Header, and add a Secondary Menu Block.
4. You will see that your Sub Menu items are now visible with the Parent Menu items and are not present in the dropdown.

Screenshots, screen recording, code snippet or Help Scout ticket

Help Scout: https://secure.helpscout.net/conversation/2304172892/378000?folderId=212385

Screenshots:
https://share.getcloudapp.com/Wnu6D00G
https://share.getcloudapp.com/2Nup7llq
https://share.getcloudapp.com/Z4uGDjjn

Environment info

No response

Is the issue you are reporting a regression

No

[cristian-ungureanu]

@RohanSharma2598 This is not a bug, it's the desired behavior.

The Secondary Menu is a single-level menu. Dropdown menus can't be used with this component.

Source: https://docs.themeisle.com/article/1237-secondary-menu#general