to display any menu Dynamics 365, you need to create a menu item as the following
create a project and add a new item, select user interface from dynamics 365 items as the below
as you see, there are multiple items items
output menu item for reports
display menu item for forms
action menu item for class
select display menu item and set name, click add
set the label (this label will display for users) and select object type form
select the object custgroup for example
save and build your solution
Now, we need to create menu for this menu item
as the same, just right click on your project and add a new item
select user interface from dynamics 365 items and choose menu as the below
set name and click add
set label for this menu and select menu item type form
locate your menu item name as the below
you configure it for specific countries by setting country region code
select the menu item, menu item type, and label
create an extension from a menu like accounts recivable as the below
add sub menu for your main menu
set properties for this menu
then build your project and refresh your browser to see changes.