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Hi intalleyvision,
If the list is stored in the same site, then to achieve your requirement, you can create relationships between lists by using Lookup column.
Lookup column is a column type that allows you to connect a list or a library to a column from another list or library you have on your site and also pull in other information from that other list and display it in the list you are connecting from.
If you want more control and customization, you can consider using Lookup column in Power Automate. While searching, I found the following similar posts that might help.
copy list itmes column value to another column sharepoint online
How to link two columns of two sharepoint lists from two different sites?
If you need any help creating workflow in Power Automate, we’ll suggest you post in Microsoft Power Automate Community for expert assistance. This is a specific channel related to issues with Power Automate.
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With sincerest regards,
Neha