We upgraded our Joomla sites from 3.4.8 to 3.6.5 a while ago and it looks like the default behavior on how the alias for Menu Item Type [Menu Item Alias] is generated has changed. And this is either a bug or a deliberate change as others are also having this issue
On 3.4.8, when I create a Menu Item Alias for 'Page 1' with a alias/slug 'page-1', it would simply autogenerate a timestamp as the alias.
On 3.6.5, if I create a Menu Item Alias for menu item 'Page 1', it tries to create an alias 'page-1', which is already used by the menu item I am creating an alias to and hence it throws a duplicate alias error.
Is this change documented anywhere so that I can see the reasoning behind it? Or is this a bug?
This is a pretty easy thing to do, it might just not be very easy to find or well documented. Follow these three steps:
Step 1: Create a new menu then go to the menu item(s) you would like to duplicate and select them all.
Step 2: Select batch, in the bottom left under "Move or copy" select the menu you created in step 1 and underneath the title select "Add to this menu"
Step 3: Select whether you would like to "Move" or "Copy" the menu items. Select process (bottom right)
Once the process is complete your new menu should be populated from an existing one.