Expired indicators remain in the Sentinel TI table until the data retention limit is reached. The records are renewed at least daily until the expiration date is reached. After the records remain until the table retention limit is reached.
I am not certain what criteria is used by the Indicators view to list or hide indicators.
This sample query might help when working with this special table:
ThreatIntelligenceIndicator
| where TimeGenerated >= ago(ioc_lookBack) and ExpirationDateTime > now()
| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId
| where Active == true