You can go to trap definitions and hit the expand icon next to the search box in the upper right. This will pull up the advanced search, then search by trap OID. That should tell you if it's there or not. I suspect it's not.
as @RPapaux mentioned you need to get the appropriate MIB file and import it into IMC. Just to make sure there is no confusion, because there often is... The "MIB Manager" function is a tool for testing with the devices, but it has no bearing on the IMC trap definitions. To import trap definitions you need to select the 'import trap definitions from MIB file' option in the trap definitions page. Either use the upload function or place the file in the directory (it's in the help text on that page) then select and compile. You should be able to search the OID in the trap definitions page after it's imported.
The fact you are not seeing anything from the switch is likely becaue it's not defined. Go to
Alarms-->Trap Management-->Filtering Trap ... and select the Unkonwn Trap Filter, which I'm fairly certain is enabled by default. Uncheck the box to disable and save. After that is changed, even if there is no trap definition in IMC you will get the trap (identified by OID because it doesn't have the details to translate). That should help determine exactly what trap OIDs are being sent and what is or is not defined. I personally always disable that option so I know if I need to import MIBs for anything.
Hope it helps
PL