Updated Keyboard mappings (markdown)

Keyboard-mappings.md

@@ -232,4 +232,10 @@ shell:
     program: /usr/local/bin/tmux
     args:
      - -u # force UTF-8 in tmux
-```
+```
+
+If you want to achieve SpawnNewInstance functionality when using tmux as shell, try the following binding to your tmux configuration file (~/.tmux.conf):
+```
+bind -n C run-shell 'alacritty --working-directory #{pane_current_path} -e tmux'
+```
+Test with "C", change with your desired key combinations.