Sometimes you might want to bring various assets — blueprints, particle systems, materials, and so on — into your project from another. To understand how you can copy blueprint to another project or import assets from another project, keep reading!
Everything described works for Unreal Engine 4 as well. You can also read a dedicated article.
Copy blueprint to another project
Using this method you can migrate an entire project into yours or move a specific asset only.
Step 1. Find the required content
Open, if not already, your Content Browser and locate the asset that you want to move. I’ll use this BP_Resource
blueprint as an example:

Step 2. Select Migrate option from the menu
Right-click the asset and select Asset Actions → Migrate…

Step 3. Confirm assets
Once you click Migrate…, an Asset Report dialog will appear, enumerating all of the assets and dependencies. Click OK.

Step 4. Find a project to migrate to
Your system file picker will open. Navigate to the target project location and select its Content folder.

If the migration succeeds, after file copying has been completed, you will see a confirmation message with the list of assets migrated.
You can then open your other project and see your migrated content.
Migration vs. Copying
If you’re unsure how migration differs from copying the files, I suggest reading another post about Migration vs. Copying in Unreal Engine.