The default keyboard does not come with its own temporary display that echoes what you type, but you can always install an alternate keyboard (I personally have the Android “Hacker’s Keyboard” which I made the default) which has a dedicated band, also used for fast complete and suggestion.
This is quite simple: you have a text to enter, and it is positioned where the keyboard would be displayed. What should the system do? Squish the rest of the screen? Scroll?
The point is that some people would object to the squishing, while others would have an issue with scrolling the display up; particularly if the display is already one that is intended to be scrollable.
You control the layout of your app, you are in charge of deciding how it should handle the display once a keyboard is shown.
In one of my app, I took upon myself to include a temporary visible field that replaces another component (through a system of “visible=true / false” logic) to echo what is being typed in a filed that would otherwise be hidden by the keyboard. In other apps, I simply made sure that no text input component are located where the keyboard would cover them.
It is under YOUR control. It is not a issue with Thunkable, you have to tools to make it work the way you prefer.