but it didn’t work for me. Perhaps another backend would help: plotly() sometimes has more options for tweaking than gr(). Inserting a line break in the title \n also didn’t work.
The best I can do for now is to resize the image. See the size argument. But then your thickness requirement is also diluted a little. So it’s not too different from reducing thickness_scaling. In other words, I can’t help very much, hopefully someone else will!