Many mobile apps implement this type of design.
These imgur screenshots show the sliding navbar for a youtube channel. Is there a proper name for this design?
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The pattern, as it appears here in the YouTube mobile app, is based on Google's Material Design language.
That navigation element is called a 'Tab Bar'
And the scrolling version is called a 'Scrolling Tab Bar'
See diagrams on this page for reference: https://material.io/guidelines/components/tabs.html#tabs-usage