OH3: Unable to add to List widget


I might oversee the obvious here, but maybe one of you can point me in the right direction.
Here is what i try to achieve:
I am building a fixed grid layout page for a tablet and so far progressing well. Now i need to configure a List widget for temperature display. But as soon as I add the List
I am trying to configure a List card wirdget, i cannot add something to that list (see gif attached (hope that works))

When i am trying the very same in the overview page, i do not see this issue and i can add jsut to my liking.
So either i am misunderstanding the whole concept, or i am doing s.th. wrong…

Can someone help me on this ?

Looks like you should file an issue on the Ui repository about this.