select - differentiate parent/child selection

introduce more accessible shortcuts

data/core.yaml

@@ -2300,6 +2300,7 @@ en:
         first: "Jump to first node"
         last: "Jump to last node"
         parent: "Select parent way"
+        child: "Select child node"
         change_parent: "Switch parent way"
     editing:
       title: "Editing"

data/shortcuts.json

@@ -159,9 +159,15 @@
             "text": "shortcuts.browsing.vertex_selected.last"
           },
           {
-            "shortcuts": ["|"],
+            "modifiers": ["⌘"],
+            "shortcuts": ["↑"],
             "text": "shortcuts.browsing.vertex_selected.parent"
           },
+          {
+            "modifiers": ["⌘"],
+            "shortcuts": ["↓"],
+            "text": "shortcuts.browsing.vertex_selected.child"
+          },
           {
             "shortcuts": ["\\", "shortcuts.key.pause"],
             "text": "shortcuts.browsing.vertex_selected.change_parent"