I figured out how to make this work for what I wanted. I discovered from this thread that I could set more than one parameter at a time using a navigation action, which I hadn’t realized before. So I set the action up to do that:
Then I used an Insight with a custom narrative to display the parameter values, with some conditional logic to choose whether to display one or both of them depending on what the value is:
ifelse(
${Region} <> 'ALL_VALUES',
${Region},
'All buildings'
)
ifelse(
${Building} <> 'ALL_VALUES',
${Building},
''
)