From there, I can use a command line MQTT client for windows and use it to publish to certain topic with payload that will trigger and automation in HA. For example…
OK. I manage to make some progress here. I managed to install MQTT client on my PC and executed the macros which publish to the MQTT broker. Here is how I did it.
Download Win32 OpenSSL v1.0.2L Light from http://slproweb.com/products/Win32OpenSSL.html and install it. Do not select the v1.1x version. During installation, select Copy OpenSSL DDLs to: The OpenSSL binaries (/bin) directory.
After installation, go to the installation directory (e.g. C:\OpenSSL-Win32\bin) and copy libeay32.dll and ssleay32.dll to the mosquitto installation directory.