To add Check if placeholder exists on Page you will need the following:
Requirements
Confluence Template Created (use the same template used to create) - if not created, follow this guide
Confluence Page Customfield
Go to a transition in Workflow Edit and Click on “Add Condition”
and then Choose Check if placeholder exists on page
Filling the form
1. Choose a template
2. Choose a Page Customfield
Choose a page customfield where the value reflects the Confluence page intended to be checked
3. Choose the checked placeholders
Click on toggle button next to each placeholder that should be checked if exists, for e.g.
Example
Admin 
CurrendDate
This condition would fail at run-time if the page still has any of (Admin & CurrentDate) placeholders
This condition would pass at run-time if the page has none of (Admin & CurrentDate) placeholders
Example
Admin 
CurrendDate
This condition would fail at run-time if the page still has any of (Admin & CurrentDate) placeholders
This condition would pass at run-time if the page has none of (Admin & CurrentDate) placeholders
4. Run as User