If you are having the access rights of workitem configuration, then you will able to add/remove workitem complexity.
To configure workitem,
1. Click on Admin on right-hand side of the header.
2. Select Company Admin.
3. Click on Workitem Configuration.
Add Workitem Complexity
To add a workitem complexity,
1. Click on Add Complexity.
2. Give an appropriate name.
3. Click on Save.
Edit Workitem Complexity
To edit complexity,
1. Click on complexity Name of the complexity you want to edit.
2. By clicking outside the edit box would save automatically.
Archive Workitem Complexity
To Archive complexity,
1. Click on Delete icon.
2. Clicking on confirmation would open pop up of Archive.
To restore complexity again,
1. Click on Archive Button.
2. Click on Restore icon next to the complexity you want to restore.
3. Click on confirmation to Restore.