Widget width in menu not stretching across the row

Hi,
The widget width does NOT stretch across the whole length of the row, even when the row has one single column!

Somewhere the width is mited by I don’t know which setting, and that’s not cool at all ..

And it’s really stupid to have for example some text which gets confined to 2 cm to the left and leaves the whooooole row space to the right empty

A fix please?

Thx