relationship lines in model view

Hi ,  marto 

According to your description, you want to create or manage the model relationships in Power Bi Desktop.

[1]You can create a relationship with autodetect:

On the Modeling tab, select Manage relationships > Autodetect.

 

[2]Create a relationship manually:

On the Modeling tab, select Manage relationships > New:

 

And for more information , you can refer to :
Create and manage relationships in Power BI Desktop - Power BI | Microsoft Learn

Thank you for your time and sharing, and thank you for your support and understanding of PowerBI! 

Best Regards,

Aniya Zhang

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