Dynamic variables are only replaced when an email is prepared for a specific contact, so the template editor shows the variable itself rather than the final text. There is no live preview inside the editor, but there are three ways to see the email exactly as the contact will receive it.
1. See it with a real contact's data
Go to Tasks and open an email task coming from a sequence. The email is shown with every dynamic variable already replaced by that contact's real data — first name, company, job title, custom fields and your snippets. What you read there is what the contact will receive. You can edit the text before sending, and the change applies only to that email.
2. Send yourself a test email
From a task (real contact data): in Tasks, on the email task, open the ⋯ options menu and choose Send test email. It lands in your own inbox with that contact's data and the template's attachments.
From the template editor (sample data): go to Templates, open or create an email template, then click Send test at the bottom. Since no contact is selected, contact variables are filled with a sample contact (Johanna Dow, Head of Sales, ABC Inc.), while your own variables — your name, product info, snippets — are the real ones. The button only appears on Email templates.
In both cases you need a mailbox connected and set as default in Settings → Integrations. If the button is greyed out, that's why.
3. Preview while writing to a single contact
Open the contact, go to the Email tab and pick a template. Subject and body are filled with that contact's data straight in the composer, before you send.
If a variable stays empty
When a contact is missing the information a variable needs, Crono warns you instead of sending something incomplete: the task shows a Missing template variable warning, and sending from the composer shows Variable value missing with the list of variables, so you can fix them or send anyway. Fill the field on the contact — or remove the variable — and the preview updates.