Hi Konstanin,
I actually ran into a problem using Connect Origins to Destinations in ArcGIS Online (Performing "Connect Origins to Destinations for many to many" analysis in GIS online? - origins and destinations must be equal). So I tried the asynchronous routing service and finally got it to work with ability to request multiple routes at a time. I explain below process for anyone needing reference. Thanks again!
ESRI documentation: https://developers.arcgis.com/rest/network/api-reference/route-asynchronous-service.htm#
Prepare data in csv with following columns:
x = longitude of stop (WGS 84 decimal)
y = latitude of stop (WGS 84 decimal)
Name = name of stop (origin -> stop -> destination)
RouteName = unique ID grouping each route together
Convert csv to json with http://www.convertcsv.com/csv-to-json.htm using template:
--Top
{lb}"features": [
--Repeating Section
{lb}
"geometry": {lb}
"x": {f1},
"y": {f2}
{rb},
"attributes": {lb}
"Name": "{f3}",
"RouteName": {f4}
{rb}
{rb}
--Bottom
]{rb}
Use Postman to complete request using parameters in ESRI documentation
Thanks again!