If you want to set a probation period, there are a couple of options. You can enable a probation period on a time policy, or you can create a custom field for a probation end date.
Probation period in a time off policy
When you create or edit a time off policy, within the Conditions section of the policy's settings, you can apply a time period where special conditions apply. You can set this to be from a specific number of days or months from the employee's start date, or select a specific date that the period will end.
Custom field for a probation end date
There is no default field for probation in an employee profile. However, you can create a custom field, and select a date type of field.
After you create the field, ensure that you assign the employee to the custom field and then set their probation end date.
📌TIP: You could create a recipe to send someone a reminder about based on their custom field probation period date.