https://docs.magnolia-cms.com/product-docs/Apps/App-configuration/App-launcher-layout.html

You can now configure the App launcher via decoration:

magnolia-personalization-personas-app/src/main/resources/personalization-personas-app/decorations/admincentral/config.yaml

appLauncherLayout:
  hiddenApps: 
    - notifications
  groups:
    - name: target
      apps:
        - name: personas-app

You can specify the order of apps by providing a complete list of apps in a group using !override:

magnolia-personalization-segmentation-app/src/main/resources/personalization-segmentation-app/decorations/admincentral/config.yaml

appLauncherLayout:
  groups:
    - name: target
      apps: !override
        - name: preview-app
        - name: personas-app
        - name: segmentation-app

You can still use the old App launcher configuration in JCR. Be aware that the order of apps comes from both the new and old configurations (first the apps in YAML, then the apps in JCR).