Hi Kaito,

The OOB Todos approval widget does not contain a link back to the actual knowledge article (KA) for the approver to see it or the details of the article.  The easiest fix is to add a link to the KA in the approval record.  What I normally do is:

1. Clone the "Todos Approval" widget and update the HTML and Server Script sections
2. Create new To-dos Configuration record for KA approvals, associate the correct widget to it
3. Either deactivate the OOB approvals To-dos Configuration and create a new one for non-KA approvals, or update the OOB one.

I'm attaching a Word document with some steps and images of options.  Hopefully this helps you.