You cannot change line type or width. If you would like to describe the use-case, we will be happy to investigate it for future releases.
A few of us on Adventurerider.com have gotten together and are designing (putting together) off-road tracks for motorcyclists. The tracks run from Massachusetts down to Florida and over to Tennessee to connect up with the TransAmerica Trail. There is a main route and several offshoots and alternates. We attempt to indicate the relative difficulty of various portions using color coding of the segments. It would be extremely helpful if we also had the ability to change the line types and widths to simply encode additional information. We, AdvRider boys and girls, also share tracks among ourselves which would benefit from the ability to provide additional encoding through line types and widths.
This project is a labor of love/passion and involves only volunteers and is in no way commercial. There are about 60,000 to 80,000 site members overall, many of whom would benefit from the additional capability.