What we could suggest you for your concrete scenario is to make the Slots you do not want to drag and drop an appointment on ReadOnly.
By design making the Slots ReadOnly
will prevent you from creating, editing or dropping Appointments in them - thus it will make it easily for the user to distinguish the restriction it has for the drag and drop of the appointments. For a more detailed information about the suggested above approach you could find on the following link from our help documentation:
We also suggest you to check the following sample project form our SDK Repository that demonstrates how to user get notified that they could not drag/drop appointments if the slots are special:
Hopes this helps.
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