Did you know that you can configure issue fields not just for Jira dates sources but for custom sources as well?
In Issue fields section, a user can configure the fields he or she wants to see on the information dialog or event block.
The Information dialog is the dialog that opens, once you click on the event.
The event block is the event itself as it is shown on a calendar.
“i“ stands for information dialog display
“e“ stands for event block display
By default, both checkboxes “i“ and “e“ of the added field are ticked. Untick one if necessary.
The issue fields configured for the information dialog display will be shown on the "Create Event" and "Edit Event" dialogs. Untick the "i" checkbox next to the field that you prefer not to appear on the dialogs.