You can define additional menu entries in the navigation menu without any link to content.
Edit the website configuration config.toml and add a [[menu.shortcuts]] entry for each link your want to add.
Example from the current website, note the pre param which allows you to insert HTML code and used here to separate content’s menu from this “static” menu
[[menu.shortcuts]]
pre = "<h3>More</h3>"
name = "<i class='fa fa-github'></i> Github repo"
identifier = "ds"
url = "https://github.com/vjeantet/hugo-theme-docdock"
weight = 1
[[menu.shortcuts]]
name = "<i class='fa fa-bookmark'></i> Hugo Documentation"
identifier = "hugodoc"
url = "https://gohugo.io/"
weight = 2