Adhidarna,
Apologies. I have an acceptable workround now and I should have posted it here before now.
When creating the export use the ‘Advanced Edit’ button. Then put your export requirements in the box that is marked ‘Enter manual export entries below’. The box is actually just to the right on my screen but it works fine. You just need to enter exports such as:
/export/nfs 192.168.1.0/24(rw,no_root_squash)
Of course you are probably not foolish enough to use no_root_squash but just put in the export options you need. Not much better than editing /etc yourself but is is a little better.
Note using this method does not magically allow Rockstor to manage the export. My NFS service reports that " No NFS exports have been created" when I have created many. However they are easier to manage for me than if they are in /etc.
I hope that helps you as well.