This guide is sort of a trick..:D
This will teach youhow to edit a transport requestthat you have already transported toQASorPROD..For example, you already seek for an approval of the TRANSPORT REQUEST that you have created..After transporting all the Infoproviders and Infoobjects that you have created, you noticed that you missed to include a single INFOOBJECT on your request..Hence, you will again seek for an approval of another transport request for that one (1) infoobject as well as re-transport all the infoproviders and infoobjects that you have already transported..
Using this trick, you need not to seek for approval for another transport request since you will be using the sameTransport Request Number..You will just edit your first transport and add that single infoobject that you have missed..
Here is the trick guyz! 
1. Go to SE10 or STMS and copy the transport request number that you want to edit.
2. Go to SE38 and run the program RDDIT076. Click the EXECUTE button (near the ACTIVATE button) or press F8 to RUN.
3. Paste the Transport Request Number (from STEP 1) and click the EXECUTE button.
4. Double click the first row and edit its STATUS; change it from R to D. Click the SAVE button afterwards.
5. Do STEP 4 on the second row. You will have the screen below.
6. Go to SE10 and double click the top row of your transport request number.
7. DELETE all ROWS.
8. Go to PROPERTIES tab. Delete all rows in the ATTRIBUTE column by clicking each row then click the DELETE ATTRIBUTE button.
9. Click SAVE.
10. Include now the objects that you want to add in your existing request by clicking the OWN REQUESTS button and locate your edited transport request.
By the way, you can also use this trick if you already released the your transport request and you forgot something to include in that transport request.
Hope this will help you guyz! 