There is an option to be able to edit toolbox documents:
"Always change the read-only status of the document before writing"
Specifies that the Toolbox temporarily modifies the read-only attribute of a file to make a change to it, such as creating a configuration for a new component size. After the change is made, the Toolbox restores access to the read-only file.
This option allows multiple users to make changes to the same document, with write access granted only briefly at the time of editing. Read-only documents for reasons of user rights or security settings in your operating system are not affected.
Which can be found here:
From Windows, click Start > All SolidWorks > Programs (version)> SolidWorks Tools > Toolbox Settings .