
I discovered an effective solution through detailed research and analysis. In Dataverse actions within Copilot, adding a lookup follows the same pattern as in Power Automate: plural entity logical name (GUID). However, the challenge in Copilot was that you could only set either a variable (GUID) or the query part (plural entity name) independently.
To overcome this, I needed to combine both the query and the GUID. I achieved this by using the Concatenate function as follows:
Here, Topic.Var3 holds the GUID of the user and is of type string. This solution successfully merges both components, enabling proper lookup functionality.
I hope this helps! If it does, please consider liking and marking it as a verified answer.