Customtkinter widgets are square in shape because it uses tk canvas, the corner_radius and bg_color are camouflaged with the background in such a way that it looks like a rounded widget. But in reality, it is a method just to hide the corners, which doesn't work for overlapping widgets. Hence, was an issue with customtkinter.
However, there is a way to fix this. (ONLY WORKS IN WINDOWS)
First, install this special package called pywinstyles (pip install pywinstyles)
You can even set opacity (partial transparency) in individual widgets like this:
This feature is not available in tkinter by default, it is exclusively made for tkinter/customtkinter, we can also do the same with tkinter widgets, see this example.
In tkinter, alpha and transparent attributes work only with the root window, but with pywinstyles we can apply both the attributes to specific widgets.
CURRENT ISSUE USING THIS METHOD
bindings or clicks over fully transparent parts don't work because the whole area is removed from the window.