Appzard is best. We can create apps quickly with so much customizations.
Kodular - Much more than a modern app creator without coding
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
RAD Studio - RAD Studio 10.2 with Delphi Linux compiler is the fastest way to write, compile, package and deploy cross-platform native software applications. Learn more.
Qt Creator - Qt Creator is a cross-platform C++, JavaScript and QML integrated development environment. It is the fastest, easiest and most fun experience a C++ developer could wish for.