Monitoring how much sick leave / absence users are taking, can be done in two ways:
By leave request:
To export all sick leave requests, split by leave type, go to time off > requests.
Here you can filter to show only sick leave requests, and this can then be exported to CSV by clicking tools > export leave to .csv.
You will need to do this separately for pending/approved/declined leave requests.
To view the total hours of sick leave each user has taken, you can use the leave balance report by going to reports > leave balance report.
This shows a table of all leave balances and how much leave each user has taken for each one. This can be filtered to only show sick leave, using the leave types filter.