> Is that by design?
Yes, that's right.
> Is there any workaround... ?
You can:
1. Import the project to your computer
2. Click on the Download button for each label to download a CSV of all of the training data to your computer
3. Use something like Excel to open the CSV files - shuffle them, and move a portion of the rows to a separate file for testing
4. Create a new project in Machine Learning for Kids
5. Import your modified training CSV files into your new project
Kind regards
D