Hi Nikolay,
apologies for the delay in response. You can set envs in app launcher configs
simply add this section to the houdini app launcher config files :
"env": {"HSITE":"some_value", ..}
You can see how it is done in a similar way when changing the launch arguments: https://ftrackhq.github.io/ftrack-connect-pipeline/tutorial/launch.html
Also You will need to alter the installed application plugin on machines, e.g.
C:\Users\<username>\AppData\Local\ftrack\ftrack-connect-plugins\ftrack-application-launcher-1.0.10\config
And remember to re-apply this configuration each time you re-install the application launcher plugin in Connect
I hope this helps please let us know if we can help any further.
regards,
Daniel