Let’s say I want to add an additional link to the admin toolbar after Reports such as Groups does.
In my_module.routing.yml I have:
my_module.admin: path: '/admin/my_module' defaults: _controller: 'DrupalsystemControllerSystemController::systemAdminMenuBlockPage' _title: 'My Module Stuff' requirements: _permission: 'access administration pages'
In my_module.links.menu.yml I have:
my_module.admin: title: My Link route_name: 'my_module.admin' parent: 'system.admin' description: 'Stuff my link does' weight: 8
I took these from the corresponding Groups module. When I clear cache, nothing new shows up in the admin toolbar or the admin menu UI settings.