Version 2018.00 adds the ability to decline meetings in calendars that are synced with Google Calendar or Exchange Server. To decline a meeting request, simply delete it. A notification will automatically be sent to the meeting organizer letting them know you won't be able to attend.
In the previous version, attempting to delete a meeting (if you didn't organize the meeting) would result in a message stating the event can't be deleted because it's read-only. There was no mechanism to decline the meeting from within VueMinder. Also, after declining the meeting outside of VueMinder, the meeting would sometimes continue to appear in VueMinder due to a bug when syncing.
Meetings can be declined by pressing the Delete key, by clicking the "Delete Event" command on the right-click menu, or by opening the meeting and clicking the Delete button at the top of the Event Editor.