The CURL request you have posted isn’t sending any body data so it wouldn’t be needed. It looks like what you have should do the job and you won’t need to toggle that JSON/RAW option so that can be disabled.
curl -v -u 407a84:api_token \ -X POST https://api.track.toggl.com/api/v8/time_entries/current
Unfortunately, I am not an IT specialist.
That’s why I bother with all sorts of things.
At least it will be easier for others like me to figure it out later!