tslint how to disable error "someVariable is declared but its value is never read"

I'm using tslint, and got the error.

'myVariable' is declared but its value is never read.

I went to the website that documents the rules https://palantir.github.io/tslint/rules/ and searched for the string is declared but its value is never read but didn't find that text. While I can and did look for settings that might be tied to this error, it shouldn't be a guessing game.

What is the configuration change needed to suppress/stop this error?

Just as importantly, when I get an error in tslint that says "this happened" how can I find what setting is used to configure or change the tslint behavior on how to handle that error?

I also did a search on the website (google search I used was)

site:palantir.github.io  is declared but its value is never read 

but a direct hit did not appear, so the answer might be on the palantir.github.io website but I just didn't (yet) find it.

How do others find the tslint variable/configuration settings that change to suppress a particular error?

Please refrain from suggesting I comment out the code that is causing the problem. I'm looking for an answer to my more general question as well as to the specific question. Thank you.

Fist question:

Edit the file: tsconfig.json, adding/modifying key "noUnusedLocals": false as follows.

{
  "compilerOptions": {
    "noUnusedLocals": false
  }
}

You'll need to restart the server.

Second question:

If it is a tslint error; VS Code shows, in the error message, the rule that's been applied.

Identifier 'doc' is never reassigned; use 'const' instead of 'let'. (prefer-const)

The prefer-const rule in this case.