For this you have to customize the layout (Alt+F12) , in the intial SAP easy access screen in Command bar last icon click on that, then click on Options , select the Expert Tab, here tick the show keys in all drop down list and save.
Now you can see Code along with Decscription.
As already suggessted by Ramesh, You can activate the Technical codes from ANY SCREEN either through ALT+F12 or by just clicking the Monitor screen icon ( the last icon next to ? icon) in the Command bar.
Go to EXPERT tab
Select "Show Keys in All dropdown lists".
These options will be applicable for all the drop down lists
Further you can Select " Short Items by Key" below the above option if you want to sort the dropdown menu options in the alphabetical order as per Technical codes, which help to group all the z option alltogether
Also SHIFT+F9 option will only display the technical name (T.Codes) in the Favorities /SAP& User Menu only