The field "Days in Sales Phase" field is not in Opportunity OWL screen and not available for selection in the "Basic Search Field".
SAP Cloud for Customer
It is not currently planned to make this field available in those areas.
You can raise a new request on our Influence page.
Please note that it is not possible for our Support Team to provide you additional information regarding the availability of this feature in a future release.
KBA , LOD-CRM-OPP , Opportunity Management , Product Enhancement