How to upload contract info for employee hired before setting employment model

Summary:

Content (please ensure you mask any confidential information):

Hello experts,

we defined for a legal employer the employment model Single Contract - Multiple assignment but for employees existing before this configuration contracts cannot be added. What should be done in this case to upload contracts for all these employees?

Thanks in advance for your time!

Regards,

Valerio

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):