seq.replaceAt

Form

{
  "op": "seq.replaceAt",
  "source": <expression:Sequence>,
  "index": <expression:Number>,
  "as": "<name>",            // optional
  "value": <expression>
}

As the specification on the plugin's main branch writes it, read again on every run.

What it does is in that plugin's specification, which ships with the plugin and changes when it releases — read it.

Add it

dotnet add package Rulealize.Plugin.Sequence