My experience with Drupal 8 step by step
First of all, you need to install Menu Export module and activate it. After that, you will have Export Menu in the Structure part.
Steps to Export & Import
1- In the Export Menu page
domain.com/admin/config/development/menu_export, you have three option, at Menu list select which menus you want to export.
2- On the Export section, export your menus.
(In this step menu setting will not be exported on YML file then you need to continue.)
3- Now you need to export system configuration from
Note: after export, you will have
menu_export.export_data.yml file that contains your menu settings
4- Transfer configuration anywhere you want, then you need to import them from
5- Then you need to import menus to your system from UI
Clear your cache
In some cases, mostly with Administration menu you need do and extra step. That you need to just open the edit Administration menu page and just saving it without any changes after this you should see your updated menu on administration as well.