Hi!
I was experiencing this issue as well when I was trying to create a combined dashboard for a lifecycle project that had multiple onboarding time points. After lots of communication with Qualtrics support we came to a solution. I will do my best to explain the steps below as it is a little confusing.
In the current project where your consolidated dashboard is, you need to create place holder open text questions in the survey form for each item you want topics for from the other projects. Use the False display logic to hide them from actually showing.
Then add these placeholder questions in the current project Text IQ configuration (In the Data & Analysis tab). Once they are added, upload the topics. In my case I just imported the same topics that I used for the actual configuration in the other projects and it worked. I don’t know if it necessarily matters since there is no actual data.
Since you already configured each item’s text IQ in their corresponding projects, you are all set. If others reading this haven't do that now.
Now in your current project dashboard go into the dashboard data. Sounds like you already added the fields needed for Text IQ for each item. For those in the current source, you should be good. For those in the other sources, you need to map the corresponding placeholder items in the current source for each item. So the current source has all the placeholder mappings and then their corresponding items from each data source.
This should work. I know it is a lot and not super intuitive, just keep in mind it is all about placeholders in the current project that allow the other projects data to display.