I am sorry.
Do you have Script at the bottom
Set to Web Publishing
I have seen and tried this feature, but the Get (ActiveModifierKeys) script steps are not colored grey. Also, the OnLayoutLoad issue was not apparent until I tried them out in Web Publishing.
In addition to the script compatibility question David addressed, you may want to review also Chapters 3 and 4 of the IWP Guide (Help > Product Documentation > IWP Guide). It gives a good overview of the major differences and limitations of IWP.
Also, several specific topics (e.g., script triggers) in the general online Help information include Notes with IWP implications. As you probably have discovered, for example, script triggers in IWP can be activated only via scripts, not by direct user interaction.
Be prepared to do a lot of thorough testing, though. Some subtleties exist around things like clicking on links, entering fields, etc. and can be affected by arrangement order (on top, or not) or tab-order inclusion. And there can be cross-platform and/or cross-browser issues with formatting, text flow, etc.