While with web forms you could build user controls (in their own project) and share between projects), MVC 5 (4.8) does not have a good option. Typically you use project templates (which copies files) or you can create custom html helpers, but they will not have post back handling. Html helpers are pretty easy to create.
In .net core, for MVC you use tag helpers or view components. For razor, you use razor components to create reusable UI components that can built into their own project.