Modules

Create groups of fields in content edit form and display.

Options for how they are grouped, like horizontal tabs or a div element.

Move description/help text into tooltips.

Core module for custom menu links.

Provides Menu Link Content entity, which can be created via the UI.

Otherwise there are only yaml and plugin based links.

Add menu links via entities other than Node.

Add fields to menu items.

Calendar view plugin with day, week, month, year displays.

Create calendars in views.

Supports Smart Date, Smart Date Recur.

Create groups with private content.

There are lots of additional modules with extra features.

The UI can be hard to work with. Modules or custom code are needed to streamline it.

Create hierarchical taxonomy widgets.