It seems that API6 does not give access to be able to change the style property of a text.
If you can add it when you first build the window view. But later, text will not have the style property available. Only the following appear:
class: Text
properties:
align
font
height
text
tooltip
visible
width
methods:
__STRICT
add_child
remove_child
The style property not found! It seems that it is necessary to implement it in the API…
It has probably been an oversight when updating API5 to API6. Remember that the style property of the class text is new in API6, and was not available in the old API5.