Is it possible to add an empty start location and an in-between stop?

[astridx]

I want to provide a link with an in-between stop via osrm on a website. Is it possible to add a blank start location text field, so that a website user can enter their address or current location?

Currently I use this link which does not offer the empty start test field

https://map.project-osrm.org/?z=12&center=50.349451%2C7.221755&loc=50.279649%2C7.222463&loc=50.272885%2C7.265739&hl=de&alt=0&srv=0