Milestone date mentioned next to milestone in de calendar

Is it possible to add a remark as the date of an appointment to that milestone, in order to be visible in de Gantt / calendar view?
I know I can add a column next to the tasks where it’s stated the start or end date of a task/milestone, but I would like this to be visible only on milestones and in the calendar/bars itself.

Thank you.

It sounds like you’re looking to add a label to milestones in your Gantt chart, which is definitely possible! Information about adding labels to the Gantt chart is available here:
https://support.omnigroup.com/documentation/omniplan/mac/3.7/en/working-in-task-view/#view-options-in-task-view