A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
Dear Vural Tuysuz,
Good day!!
Apologies for the inconvenience caused and please don’t worry, let’s work together on your concern and move towards a resolution path.
I understand your concern and I would like to let you know that I have tested the behavior at my end, where I am able to copy and paste the values to the Lookup column in the Grid View without any issue.
So, I would like to confirm whether you are having the same issue when you access the List in the InPrivate or Incognito window of the browser and check the behavior.
If the same problem persists, we are sorry and I believe the problem should be further investigated by the related development team, where they can collect the HAR logs while reproducing the problem and perform further investigation.
Note: I have checked the service health dashboard at the Microsoft end, where there is no related incident found.
Since you have already collected the HAR logs while reproducing the problem, I request you to connect with the IT admin of your organization and ask them to raise a new service request on your behalf, where the related development team will connect with you via phone or preferred contact methods and collect all related logs to investigate the issue further.
Reference: Get support - Microsoft 365 admin | Microsoft Learn
Note: We apologize for redirecting you to related development support team because the moderators in this community are limited with the resource for further investigation and to get a quick resolution to your problem, we requested it.
Appreciate your patience and understanding. Have a great day!!
Best Regards,
Sophia