I have completely checked your issue at our code as well as with your module.
But I think you might have misunderstand something, because in your code you have used a "tabpos" attribute under notebook then you got a different behavior on web-client and in gtk client.
GTK displayed a proper and it's working fine but in web-client it's not working because we need to implement this feature in web-client which is already considered as a "Wishlist" on lp:901644.
Hello Manfread,
I have completely checked your issue at our code as well as with your module.
But I think you might have misunderstand something, because in your code you have used a "tabpos" attribute under notebook then you got a different behavior on web-client and in gtk client.
GTK displayed a proper and it's working fine but in web-client it's not working because we need to implement this feature in web-client which is already considered as a "Wishlist" on lp:901644.
So I am closing this issue for the GTK-client.
Thanks for reporting!