Well actually it's just a single string so it might not count as a full blown tassle.
I was a bit dismayed when I discovered that my lovingly used 2016 Zero DSR had no way to prevent movement whilst parked on an incline.
I set about fastening a makeshift front brake manual lock consisting of a 3/8" copper tube coupling zip tied to the master cylinder.
I found a rollerball pen barrel that nicely fit inside the coupling & also fit behind the hand lever once squeezed to keep pressure on the master cylinder thus creating a hand brake.
The pin barrel was then replaced with a smart device stylist so I could use my phone (responsibly while parked) with my gloves on.
This arrangement worked well until I put hand guards on at which time I lost the clearance required for the stylist so I went without a parking brake until a few days ago when I realized all I needed was to tie a string around the end of the handle bar/hand guard area with a loop on the other end that fits around the hand lever.
Squeeze the hand lever then slip the string over its end & the front brake master cylinder retains pressure.
This works for my needs but may not for everyone else.
Use with caution & at your own risk.
The string doesn't interfere with the throttle & is not very noticeable after I tinted it black.