I am trying to learn Qt version 6, and I'm at a point where my book has me importing QtQuick Controls. The book says to click on the "Imports tab" in the Library pane, and shows a screenshot containing the tab. (Virtually every web source I've been able to find says the same thing, with a similar screenshot.)
Unfortunately, my installation of Qt-Creator, version 4.15.1, installed with Qt 6, does not have an Imports tab on the library pane. This is what my Library pane looks like:

Yes, it appears that the controls have been imported, but I didn't do it through the UI, it happened during an experiment. What got the controls imported was:
- I hand-edited the
.ui.qmlfile to add the line
import QtQuick.Controls 2.4
- I built the project
This resulted in the QtQuick controls appearing in the Library pane.
Surely this is not the normal way of importing controls, is it?
If I'm understanding correctly, you want Qt Design Studio to import modules for you from the UI.
Simply click here then:

Also, if your project was made with Qt6, there's no need to add the version in the import statement.
I hope I was of any help :)