Is there a Python programming environment like VB6 [meta-GUI: GUI making GUI]

[snippsat]

From what I have gathered, I create the form in the designer, save it as a .ui file, then use PyQT to convert the file from a .ui to a .py (basically from xml to py).

You can convert it with pyuic5.exe which is placed PyQt5\Scripts folder.
From command line.

pyuic5 app.ui -o app.py

But that's not needed,can load ui file straight into code.

from PyQt5 import uic, QtWidgets
import sys
 
class Ui(QtWidgets.QDialog):
    def __init__(self):
        super().__init__()
        uic.loadUi('app.ui', self)
        self.show()
 
if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    window = Ui()
    sys.exit(app.exec_())

I can then open the .py file in whatever editor I like (notepad, pycharm, whatever) and add the code for the different elements on the form.
Correct?

Yes where you work from is up to you.
I have switch from Atom to VS code.
I am impressed bye this free editor,i have quick  review here.

Take also a look part-1 and part-2 for working in Windows.