How much time does it takes for the pending external validation to be completed
It is a step that needs manually approve, it takes as long as the workflow step owner needs.
@Swarna12 @JackFan is correct. This is an approval step that occurs outside of SAP Concur and is done by a person. Each company that uses this feature has their own service level agreement time frame. Best thing I would recommend is ask your direct manager if they have any information on what the amount of time usually is for this to be completed at your company.
So why am I seeing this for the first time today?
@mbjes4324 That isn't something I can answer. I can speculate and say that it is possible that your company decided to implement this recently. This is something better answered by someone at your company. I would start by speaking with your direct manager and see if they can shed any light on this.