Here the link >
I am not sure your SRC version so you can access the SRC customization guide and check if if is possible. Hope it helps
Customer Support Engineer
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I found that this is GL - $G.callbackType and now i can control list of vlaue
1) Can i control what list must use SRC ?
2) Can i set default value in SRC for this field (to prevent the user from selecting the most frequently used value from the list, or if there is only one value in the list) ?
3) How can remove this field from SRC (if it's possible) ?
you can remove this field from Tailoring -- > SRC tailloring there you will see section for support and service catalog open that by double clicking.
Then fields used will be listed there you add and remve , edit.