How do you make this?

VeeExcelLearn It all depends on your requirements. But, if you are trying to create a custom solution for SharePoint online modern experience, you can create it using SharePoint framework.

SharePoint framework offers different components (web parts, extensions, etc.) which will fit for different scenarios/requirements. I will suggest you to go through above documentation link for detailed information.

Also, check SPFx web part samples submitted by community members which will give you idea about the capabilities of SharePoint framework: sp-dev-fx-webparts samples 

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