Assembly Definitions

The package does not have assembly definitions, but you can add them with all required references.

Why no assembly definitions by default:

changes in the .asmdef files are lost with the package update
supported third-party packages do not use assembly definitions, so they cannot be referenced to be used in a separate assembly
version defines works only for Unity packages, so only direct references to assembly definitions are available

Recommended Settings

asmdef for the runtime should be created in the New UI Widgets folder
asmdef for the editor should be created in the New UI Widgets / Editor folder
references to TextMeshPro and InputSystem should be added if you use them

asmdef for the runtime — Runtime

asmdef for the editor — Editor