Functional style, instead of adding conditional logic in the template use the fact that [] is a monoid. [a] + [] = [a] and [a] + [b] = [a,b]

navigation.haml

:ruby
  getAttrs = ->(link) {{href: link.fetch(:href), class: link.fetch(:class)}}

  # Added to prevent typos in `tab_to_conf` and `mkLink`
  events, following, calendar, overview, manager, followers, widget =
    %w(events following calendar overview manager followers widget)

  tab_to_conf =
    { calendar  => [t('users.profile.calendar'), user_path(user)],
      following => [t('users.profile.following'), following_user_path(user)],
      events    => [t('shared.header.menu.my_events'), events_user_path(user)],
      overview  =>
        [ t('user_account.events.overview_events_text'),
          events_overview_user_path(user) ],

      manager =>
        [ t('event_manager.login.headline'),
          events_manager_user_path(user)],

      followers =>
        [ t('users.profile.followers', count: followers_count),
          followers_user_path(user)],

      widget =>
        [ t('user_account.events.embed_widget_events_button'),
          events_website_integration_user_path(user)]
    }

  # Using Curry here, Just using a closure might be more clear
  mkLink =
    ->(current_tab, tab) do
      t, h = tab_to_conf.fetch(tab)

      {title:t, href:h, class:('muted' if current_tab === tab)}
    end
    .curry
    .(current_tab)

  user_links =
    is_current_user ?
      [ mkLink.(events),
        mkLink.(overview),
        mkLink.(manager),
        mkLink.(widget) ] : []

  public_links =
    [ mkLink.(calendar),
      mkLink.(followers),
      mkLink.(following) ]

  links = user_links + public_links

.profile-navigation__links.text--center
  - links.each do |l|
    %a.profile-navigation__link.chamber--right{getAttrs.(l)}= l.fetch(:title)

Pseudo example in Javascript

const
  common = // :: [Link]
    [home, about, status ...],

  user =  // :: [Link]
    isAdmin
      ? [settings]
      : [],

  private = // :: [Link]
    isAdmin
      ? [admin, ...]
      : [],

links = // :: [Link]
  common
    .concat(user)
    .concat(private)
  // common + user + private | common <> user <> private | common  `mappend` user `mappend` private

toLink :: Link -> Html
links.map(toLink) // :: Html