As you know, you can lock/unlock transaction codes via SM01. But, how do you go about viewing the transactions that are locked in the system? You need to look in field CINFO of the table TSTC.
Within SAP, you can either SE11 or SE16 to browse the table contents. Make sure you enter ‘A0’ as the “Hex01 data element for SYST” starting value and ‘A9’ as the ending value. This will list all the transactions locked in the system.