If your on *NIX or mac it's easy to do using the duetwebapi python interface.
https://pypi.org/project/duetwebapi/
install via
pip install duetwebapi
create a file script to execute (up.py for me)
#!/usr/bin/env python3
from duetwebapi import DuetWebAPI as DWA
import sys
###################################
# Create API link
###################################
hevort = DWA('http://hevort.local')
###################################
# REST API methods
###################################
#hevort.send_code('M115')
hevort.upload_file(sys.argv[1])
next tell s3d to use your pretty new python script by adding this to the
Additional terminal commands on the scripts tab.
/usr/local/bin/python3 /ssd/scripts/up.py "[output_filepath]"
Now just slice and save in s3d and it's in DWC. You can use the send_code I commented out to send and code so you can in fact start it also, I just opted not to at this point...