In ABAP Managed Database Procedures there are scalar and table variables available, but no structures.
Scalar variables can be inspected in the Variables view of the Debug perspective while table variables can be inspected in the Data Preview tool. Additionally there is the option to mouse hover over variables in the source editor.
To view the variable values within the SQLScript...
The types of the variables are native DB types like VARCHAR. If you want to see input/output parameters after the type mapping to ABAP data types, you can use the ABAP Debugger.