F5 iRule Editor

I can't recommend enough that you don't use the iRule editor, there are much better tools availible now without the risk of making changes directly on the box.

Take a look at Andy's code share with information how to use MS Code as an editor. This is what I use for writing iRules and it is far superior to the editor

https://devcentral.f5.com/s/articles/iRules-Development-Environment?page=1