Next time you're in the IMG maintaining config, look at the object(s) attached to the transport request once you've finished and saved your work to a transport request -- this information is needed for the next step. Usually, there will be only one object attached to the request, unless you bundled changes to many customising items in the one request. If there are more than one, try out the steps below for each one in turn.
For view objects (names begin with V_*), try going to transaction SM30, enter the table/view name and click Maintain. If the object is a T* table, put a 'V_' in front of the table name, and try the above anyway. This method works for most view tables for T* config tables.
If SM30 doesn't work, try the following:
1. Go to transaction SOBJ
2. Click on Display
3. Scroll down the object list until you come to the object you are looking for (if you are looking for a T* table and don't find it, try looking for a corresponding V_T* object)
4. Select the object by clicking on the table row
5. Click on Subobjects from the Navigation menu above
6. In the resulting Subobject list, if you see a Documentation object with a name 'SIMG_*', double-click it to bring up the details of the Subobject
7. In the Sub-object Details screen, look for a transaction code shortcut (sometimes step 5 brings you straight to this screen)
One thing that requires you to enter the IMG for maintenance, for which you won't find a shortcut for by following the above instructions, is report trees. However, if you go to transaction SERP you can maintain any report tree directly.