Can Increase list view threshold view in SharePoint Online which by default is 5000?
Increasing the List View Threshold in SharePoint Online is not permitted.
This article has some suggestions for working around the LVT - http://www.markrackley.net/2014/10/22/working-around-that-pesky-list-view-threshold-in-office-365-sharepoint-2013/
No, Its not possible to change the list item threshold value, What happens if you have 5001 items? This little gem of an error pops up: "The number of items in this list exceeds the list view threshold, which is 5000 items. Tasks that cause excessive server load (such as those involving all list items) are currently prohibited." In a nutshell, you will not be able to upload more items until you go below the threshold.
The official reason listed by Microsoft is: "This issue occurs because SharePoint Online uses the Large List Resource Throttling feature. By default, the list view threshold is configured at 5,000 items. When the defined item limit in a list is exceeded, the message is displayed."
This is one of the key difference between O365 and On Premise SharePoint. With On Premise SP, you can actually increase the threshold limit and get around that error, but it does have a consequence as your SQL Server will take a significant resource hit.
Why is 5,000 such a magic number? To minimize database contention, SQL Server often uses row-level locking as a strategy to ensure accurate updates without adversely impacting other users who are accessing other rows. However, if a read or write database operation, such as a query, causes more than 5,000 rows to be locked at once, then it's more efficient for SQL Server to temporarily escalate the lock to the entire table until the database operation is completed. When this lock escalation occurs, it prevents other users from accessing the table. If this happens too often, then users will experience a degradation of system performance. Therefore, thresholds and limits are essential to help minimize the impact of resource-intensive database operations and balance the needs of all users.
As I alluded to earlier, you will not be able to delete the list and/or the site unless you manually delete the items first. The problem is that once you exceed the limit, the items will not render at all. You are just left with an error message and no visible way to get to your data.
To overcome this, you can follow the links provided by @BhaskarDhone
In SharePoint online list view threshold can not be modified. As answered by Erik.
Sharing two workaround that may help you out :