Not true. If you highlight multiple consecutive rungs prior to online edit they can all be modified.
When it comes to edit/test/undo edits the AB software is easier to use. BUT, in OMRON you can just as easily do this by using a N.C. contact that spans the OLD rungs and a N.O. contact for the NEW code. Once compiled, the OLD and NEW code can be tested by setting the contact ON or OFF. Once satisfied that the change
is OK then delete the rungs of the OLD code and remove the ON condition ahead of the NEW code.
Not quite as easy as the AB software but works just fine for me.
The ONLY disadvantage of this method is that the OMRON code does NOT readily allow ACCEPT/UNDO of new edits. Also if NON-CONSECUTIVE rungs must be edited then the test contact conditions N.O./N.C. must be applied to rungs where edits are made.
A little more convoluted than AB but works just fine.