You have need for common test keywords or scripted methods across projects in Testcomplete.
You need that they are only to be maintained in one place.
You can put your shared script units to a separate folder on the hard drive. When you need to link them to a new project, open this folder in the Add Existing item - Script dialog and press the Ctrl+A shortcut to select all files in order to avoid adding them one by one.
You Can however also pick the items one by one.