This is similar to: An Editor Toolbar Button to Insert User Signature with Timestamp
Your code would look like:
\define mytext() <<strex content:"$(mycontent)$" id:"$(myid)$">>
<$vars
mycontent={{{ [[$:/status/UserName]get[text]else[Anonymous]] }}}
myid=<<now "YYYY-0MM-0DD-0hh:0mm:0ss">>
>
<$action-sendmessage
$message="tm-edit-text-operation"
$param="insert-text"
text=<<mytext>>
/>
</$vars>
The trick is to:
- create your /define macro using $(name)$ substitution
- defined the $(name)$ values using $set
- insert the now substituted values into your edit-text.
My noob $0.02 
Jeff