Time off added on timesheet do not list under the Historical Time Off section in Web TimeSheet Administration. This section would only list the time off that require booking. 
The time off that was added on timesheet can be viewed or edited or deleted only by opening the timesheet period when the time off was added to the timesheet.

Administrators can view / edit / delete all the users' past, present and future timesheets under the Historical Timesheets section in Web TimeSheet Administration.

Users can view / edit / delete their time off entries from their current or future timesheet but however to reopen their past approved timesheet, they should have the Allow reopen of timesheet after approval option enabled in permission enabled for the user.