This is a paid asset, but now you can download Project Asset Manager for FREE, but please remember this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
Detail this asset from Unity Store: Original Link
Project Asset Manager v1.42.8143
Project Asset Manager is a tool to help you manage your offline asset collection alongside your asset store collection.
Project Asset Manager is an editor tool which helps you manage your assets packages and project code. Work with the Unity Package Manager,Git, and file repositories (both local and network) in a single unified interface.
Website: https://unityassets.doubtech.com/unity-asset-manager/
Discord: https://discord.gg/ny5kkn323g
Package Management
Quickly install many assets at once
Track what versions of assets you have installed so you know when you need to upgrade
Easily manage an offline repo of assets. Add a directory containing unity packages and all of the packages under that directory will show up in the package manager. This makes dealing with assets downloaded from third parties like the Synty Store or CG trader easier.
Bookmark github based package manager packages for easy import
Save import time, search for prefabs in assets you haven’t imported yet
Essential Packages
Easily and automatically import a set of packages for all of your new projects that includes the tools you need.
Selected packages automatically get installed after installing Asset Manager
Audio Files
Keep track of audio files in your project as well as on your filesystem
Search through your local audio asset library and preview audio files before importing them (Only wav supported on Windows, more support pending).
Credits
If you use Asset Manager to import your assets you can easily generate credit files