Choosing a text editor for coding is a very personal choice. Some have "too many" features, others are too simple. You may need to try more than a few to find one that you like working in, but it's not until you start on an actual project, that you'll be really able to tell.
Thunkable is based on a very similar free tool call MIT App Inventor. Because lots of people create Extensions for it, that also work with Thunkable, you can find extra code, called Extensions which do everything from rotation detection, to sound analysis, to QR code recognition and connecting to other devices.