How to create ad-hoc notifications

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Good day, 

Could you please advice if there is a possibility to create ad-hoc notifications in HCM Cloud not related to a special workflow and without any trigger and send them to a determined group of employees. 

For example, in the beginning of the year HR specialists would like to send the reminder to determined employees (but not to the whole company)  to plan their vacations for the year. Each year the text and list of employees can be different. 

Thank you!