Add another main navigation block for 2nd-level menu

And place in the secondary_menu region we output in the node template titlebar region
thanks to our https://www.drupal.org/project/regionincontent module.

config/sync/block.block.agarica_main_menu.yml

@@ -5,6 +5,7 @@ dependencies:
   config:
     - system.menu.main
   module:
+    - block_visibility_groups
     - system
   theme:
     - agarica
@@ -22,5 +23,10 @@ settings:
   provider: system
   label_display: '0'
   level: 1
-  depth: 2
+  depth: 1
-visibility: {  }
+visibility:
+  condition_group:
+    id: condition_group
+    negate: false
+    block_visibility_group: ''
+    context_mapping: {  }

config/sync/block.block.mainnavigation.yml

@@ -0,0 +1,30 @@
+uuid: add6196e-3612-4143-a31f-3ad79d359c0d
+langcode: en
+status: true
+dependencies:
+  config:
+    - system.menu.main
+  module:
+    - block_visibility_groups
+    - system
+  theme:
+    - agarica
+id: mainnavigation
+theme: agarica
+region: secondary_menu
+weight: 0
+provider: null
+plugin: 'system_menu_block:main'
+settings:
+  id: 'system_menu_block:main'
+  label: 'Second-level main navigation'
+  provider: system
+  label_display: '0'
+  level: 2
+  depth: 1
+visibility:
+  condition_group:
+    id: condition_group
+    negate: false
+    block_visibility_group: ''
+    context_mapping: {  }