The tab "ViewAddons" in Designer Schema Editor is missing when you click initially on SQL view.
The issue is caused by the known product defect 29185.
This defect reappeared with Identity Manager version 8.1.3, which is documented and fixed by defect #33171.
Just click on another item inside of the form. Then go back to the root node and the 'ViewAddons' tab will be visible.
There is a fix for this issue. Please open a Service Request with One Identity Manager Support, specifying the defect ID #29185 or ID #33171
Please Note: 29185 was fixed with version 8.1.1. Defect 33171 (introduced again with 8.1.3) will be fixed by version 8.1.4.