Merge Tag Previews
With merge tag previews you can display your merge tags replaced with a testing data in a preview. You are also able to send a test email with the testing data.
INFO
Please enable Smart Merge Tags in order to use Merge Tag Previews.
All you need is to add the following to Topol Options:
js
enableMergeTagPreview: true,
When you navigate to preview you can see following UI:

Only merge tags used in the template are shown.