This is the limitation of the editor, hard-coded within.
2 solutions for this:
1-use triggers to cause the desired doodads to apper on game time 0.01, effectively nobody will ever notice
2-download another editor, most custom-made editors had been released from the restrictions. (find in tools section)
I prefer option 2, but be advised that there was a reason for the restrictions from the firstplace, too many doodads will cause strain.