Chummer allows you to link your Contacts and Enemies to other save files. To link a Contact or Enemy to a save file, locate the desired Contact or Enemy, click on the chain icon, and choose Attach Character.
Select the appropriate save file from the window and click Open.
The save file is now linked to the Contact/Enemy. To view the character, click on the chain icon and choose Open Character.
You can also remove the link by clicking on the chain icon and choosing Remove Character. This will only break the link between the Contact/Enemy and that save file, it will not delete the file.