As per my understanding, if two or more team members try to edit same product backlog item (PBI) simultaneously then changes saved first will update the PBI and others will get notification to discard their changes.
Is VSTS provides a way (in SCRUM work process) to enable edit lock notification to other users as soon as they begin to edit any PBI instead of notifying them when they are done with changes at the time of saving?
Yes, when someone saved their changes first, others may get an error as below:
TF26071: This work item has been changed by someone else since you opened it. You will need to refresh it and discard your changes.
However, there are multiple fields in a PBI workitem.You will only see the message when the same field is changed by 2 different users.
When different fields are changed by different users, we merge the changes.
There had been a related uservoice: Merging support for WorkItem Changes and got DECLINED· If you really need a feature like the lock notification, feel free to submit a new uservoice, TFS PM and Admin will kindly review your suggestion.