Sorry about this.
The reason for me pushing the approach of uploading photos somewhere else, and then (by dragging-and-dropping) giving me the URL, is because it keeps my running costs for the site down.
Storing a small bit of text (the web address for the image) is *so* much cheaper for me than storing the bytes for a photo.
It's orders of magnitude cheaper.
In the interest of keeping the site free, without charges or adverts, I have made a few compromises like this - even though I know it'd be nicer/easier for you if I just let you upload images.
Sorry for the inconvenience this causes.
If it's a blocker for you, you may prefer to use Teachable Machine to train the model, which you can then use Machine Learning for Kids to open in Scratch