I couldn't find a way to insert into the revision block. What I did as a test was enter 3 revision entries with descriptions of TEST1, TEST3 and TEST4. To enter TEST2 in place of TEST3, I went into edit, clicked on TEST3, cut the entry (TEST3) then changed it to TEST2. Edited TEST4 entry, pasted TEST3 in front of TEST4, then cut TEST4 and added a NEW line for TEST4 entry which was pasted in from the previous edit.
I hope that makes sense - as far as I can tell, that's about as good as it can get.
GTAC (Siemens helpdesk) does have a GM Toolkit specialist. So you can call them for GM Toolkit-related topics. If you have a maintenance agreement that is current, I feel it would be worth your time to call GTAC and see if you can make an Enhancement Request for this and give them your take on adding an INSERT option for the Revision Block and anything else that might fall into this category.
The newer roll sized formats which I am making use Tabular Notes and don't error out when manually editing them, which is nice. It appears to me the 11X17 drawings are still using geometry and text which is a bit dated.
Tim Flater
NX Designer
NX 11.0.2.7 MP11 Rev. A
GM GPDL 11-A.3.5
Win7 Enterprise x64 SP1
Intel Core i7 2.5GHz 16GB RAM
4GB NVIDIA Quadro K3100M