If you want to see a transparent preview
of the part when you drag it from the Toolbox library, add a mate reference
to the part.Use Add to Library to add parts to the SolidWorks Toolbox library. You can add parts to existing SolidWorks Toolbox groups, or you can create your own groups.
Administrators can control who is allowed to add parts to a shared library. See User Access Control in Configure Data - Settings.
If you want to see a transparent preview
of the part when you drag it from the Toolbox library, add a mate reference
to the part.
To add to the SolidWorks Toolbox library:
Click Add to
Library 
on the Task Pane Design
Library tab.
Set options in the PropertyManager.
Click 
.