Actually I was trying to switch from Textual to Graphical Configuration as recommended. But It seems very hard and frustrating. Here’s another example…
The parameter active_low="y" as mentioned in the Docs can not be set in the new graphical Configuration. Am I missing something? 
No your missing nothing. See [mcp23017] The active_low channel configuration parameter needs to be added to config.xml · Issue #5242 · openhab/openhab-addons · GitHub
But the mcp23017 binding doesn’t work either on oh3: [mcp23017] pi4j not compatible with Java 11 · Issue #9503 · openhab/openhab-addons · GitHub
Thank you. Will wait then…