I don’t think what you’re experiencing is directly related to the Todoist Sync Plugin, but is more a general matter of markdown formatting. Codeblocks need to be the first element, and when you do - ```todoist, it’s just something weird markdown code. This can further be seen with the code block actually starting below your red frame with the next bullet point.
So one of adressing this is possibly to format your text more like the following example:
- List item 1
- List item 2
```js
console.log('Another block')
```
- List item 3
That is indent the code block on a new line, to match the indentation level of the list. In my cases this gives the illusion of the block level being a part of the list, and not outdented to the main level.
A few links talking about similar issues:
- Live Preview: Better support of code blocks in lists - #4 by s-kyy
- Code blocks nested in lists render in editor as if at top-level - #10 by chansey97
- Code blocks in list error
Hope this helps, and gives you a way to handle your situation.