Can't get an action to appear on a Mail memo in iNotes

I have a development server running Domino 9.0.1 FP8. I have placed all the iNotes files, including Forms9_x.nsf on the server in the iNotes directory. I’ve spent time reading instructions, including here: https://www-10.lotus.com/ldd/dominowiki.nsf/dx/inotes-customization-changes-for-8.5 https://www-10.lotus.com/ldd/dominowiki.nsf/dx/inotes-customization-changes-for-8.5

But I can’t seem to get an action to appear in the Mail memo. Ideally, I want to display two more custom subforms on the mail memo, but I thought I’d start with displaying a button. No joy. Can someone post sample code demonstrating how to display a custom subform on the top and bottom of the Mail memo? These custom subforms will be in the database itself, or I can add them to Forms9_x.nsf, whichever works.

EDIT: Will this work? In the l_ShimmerSkin-h_MailPage subform, adding this:

Thanks in advance!

Subject: here’s some code

I want to add an action button to the mail memo in iNotes, that displays in a browser. As a test, I have added code on the Custom_JS_Lite subform, in the Custom_Scene_Actions_Lite function:
var a=[{title:“hello world”, find_id: “new”, id: “hello1”,
before: true, action:“alert(‘Hello world!’)”,
help_text:“some hover text”}];
addActionsLite(s_MenuID, true, a);

But this does nothing. I don’t see the “hello world” action anywhere.

How exactly can I add an action button? I will cross-post this, the server is 9.0.1, and my Designer client is 8.5.3.