Hello,
by searching the forum, I have found an example of batch script that can be used to start codesys projct by temporarily setting env variables.

However, I'm not sure how to modify this to start Codesys 3.5.20 and whether or not I need to specify "profile" with Codesys version at all.

@echo off
SET PROJECT=D:\TestScripts\Data\OnlineTest.project
SET VARIABLES=POU.testint,POU.testoutput
start /wait CoDeSys.exe --profile="CoDeSys V3.4 SP3" --noUI --runscript="D:\TestScripts\Forum_Environment.py"

I have tried the following just to open the test project:
SET PROJECT=C:\TEST\Example.project start CODESYS.exe --profile="CODESYS V3.5 SP20 Patch 2"
But I'm not sure how to specify this project to be open after py script is executed.
The py script should first add required library to the project and then project should be open.