let's try that

_includes/header.html

@@ -4,7 +4,9 @@
     <ul>
       {%- for path in page_paths -%}
         {%- assign my_page = site.pages | where: "path", path | first -%}
-        {%- if my_page.title == '/git' -%}
+        {%- if my_page.title == 'mainsite' -%
+          <li><a href="https://pickmy.org/">pickmy.org:~$ - </a></li>
+	{%- elseif my_page.title == '/git' -%}
           <li><a href="https://git.pickmy.org">/git</a></li>
         {%- else -%}
         <li><a href="{{ my_page.url | relative_url }}">{{ my_page.title | escape }}</a></li>

menu.md

@@ -1,6 +1,6 @@
 ---
-title: pickmy.org:~$ -   
+title: mainsite
 layout: default
-permalink: https://pickmy.org
+permalink:
 ---