@Anonymous
The DefaultSelectedItems property (DSI) of a Combobox expects a Record or Table of Records (depending on the settings of the combobox).
The Record schema of the provided record MUST match the schema of the Items property.
In your case you are setting the Items to an entire table - which will be a table of records with a schema based on the schema of [dso].[AzureADGroupsTable].
Then your DSI is set to a table with a single column schema with each column, most likely, containing a text value. This will never match! It will give you an error but it will not match.
I do not know what dependencies you have on the Combobox selected items, but if you are ONLY utilizing the displayname column values, consider changing your Items property to:
ShowColumns('[dbo].[AzureADGroupsTable]', "displayname")
Now, for your DSI property...you need to reference a single record in your ModifyProject table. Currently you are referencing the entire table and thus you will get an entire table, which again will not match.
So, once you determine how you will get to a single record in that table based on your App (I'd recommend approaches, but I do not know your scenario at this point) then you can use that in the DSI.
{displayname: yoursingleprojectrecord.project_lead}
The above will give you a proper selection in the combobox.
I hope this is helpful for you.
