Are you trying to make the widget appear visually larger or lengthen it like a lifebar increasing in capacity or something to that effect?
For the former, you can simply change the render transform scale. For the latter we’ll need more info - what’s the widget’s parent? By default it would be a canvas panel, so assuming that to be the case, you’ll first have to get the widget’s slot, cast it to a canvas panel slot, then set the desired size from there.