I have a menu with more than 100 items in total and it is very slow to manage all those, slow respond and slow saving. Is there any plugin to somehow improve performance and make my life easier in a big number of items?
WordPress menu performance is slow when lot of items
There is no plugin to improve performance, its related to server and performance of hardware. You can obviously tweak your WordPress settings for this. You man also opt to migrate to a powerful server which can handle/process all these queries. You can also tweak your database settings.