Hello M.,
Now with style (from v1.2022.2+...), you can style `duration arrow`, just before duration arrow (not on global) as:
<style>
arrow {
LineColor green /' (a) color tagging the arrow '/
LineThickness 3 /' (b) thickness of just the duration arrow '/
LineStyle 6;3 /' (c) use other linetypes '/
}
</style>

If that can help,
Regards.