Please follow the steps below :
1. Go to workspace > configuration, in the CAD menu and select CIVIL_SUPERELEVATION_RULES_DIRECTORY configuration variable.
2. Click on edit and change the path from C:\ProgramData\Bentley\Civil\Standards\8.11.9\en\Superelevation\SRL to C:\Program Files (x86)\Bentley\MX V8i (SELECTSeries 3)\MX\MFW\IN_Styles.
3. Save the changes. Exit out of MX
Restart MX and check the srl files should be available.