See Details for Inactive Structures

The following script will list structure names that weren't accessed for 6 months, its owner, and last opened value.
import com.onresolve.scriptrunner.runner.customisers.WithPlugin
import java.time.Duration
import com.onresolve.scriptrunner.runner.ScriptRunnerImpl
import com.almworks.jira.structure.api.StructureComponents
import com.almworks.jira.structure.api.permissions.PermissionLevel

@Grab(group = 'com.almworks.jira.structure', module = 'structure-api', version = '*')
@WithPlugin('com.almworks.jira.structure')

def sc = ScriptRunnerImpl.getPluginComponent(StructureComponents)
def sm = sc.getStructureManager()
def sps = sc.getStructurePropertyService()

def currentTime = System.currentTimeMillis()
def structures = sm.getAllStructures(PermissionLevel.VIEW)

//structures not accessed for 6 months
def sixMonthPlusOldStructures = structures.findAll { structure ->
  def lastPolledMillis = sps.getLong(structure.id, "lastPolledMillis", 0)
 return lastPolledMillis > 0 && Duration.ofMillis(currentTime - lastPolledMillis).toDays() > 180 //6 months ~ 180 days  
}.collect{
    [it.name, Duration.ofMillis(currentTime - sps.getLong(it.id, "lastPolledMillis", 0)).toDays(), it.owner]
}

//structures that were created but never opened
def createdButNeverOpened = structures.findAll { structure ->
  def lastPolledMillis = sps.getLong(structure.id, "lastPolledMillis", 0)
 return lastPolledMillis == 0
}.collect{
    [it.name, it.owner]
}

return [
    sixMonthPlusOldStructures: sixMonthPlusOldStructures,
    createdButNeverOpened: createdButNeverOpened
]