I've managed to fix these errors

CultureNode.cs


private bool openPicker = false; // 1. add this

int currentPickerWindow = GUIUtility.GetControlID(FocusType.Passive) + 100; //2. remove this

icon.RegisterCallback<MouseDownEvent>(evt =>
{
if (evt.button != 0) return;
openPicker = true ...

Hey there! As said in Subject, I'm new to this asset.

I like the videos, how it could look like etc but I have some problems with it.

On a fresh installation I've gotten this
https://imgur.com/a/z0qJFY1
after clicking on "New Culture"

So I cannot complete video tutorial as this is first step in ...