The blue hyperlinked click here text is how clients will access the online form, e.g. pre-work, feedback, etc. If this is deleted when editing the email, a link with the text 'Please click here to read and submit the document' appends to the end of the email to ensure clients can access the form.
 
If you accidentally delete the click here link, you cannot add the link back in by typing the text ‘click here’. However, you can type {doc_link} to add the link back in. This is what we call a merge tag and it creates the link from your email to the online document. After clicking the Next or Action buttons on the document, you'll see in the Email preview that your {doc_link} text has converted to a click here link.