I have some periodic things I do during the day, and have found the "suspend" feature for reminders useful for the purpose.  If I need to do something every 3 hours, I create an event 3 hours into the future and then suspend it repeatedly for 180 minutes.  When such a suspended reminder is pending, I don't believe there is any way to see at what time it will trigger, and I sometimes would like that information.  Also, I sometimes want to change the timing after the fact – e.g. if I got distracted and suspended the reminder without actually doing the thing associated with it, I might want to adjust it to trigger 3 hours from the time I actually did the thing.

Some UI ideas:

1. You can already set and manipulate multiple reminders in the event dialog, each reminder having a separate line.  This could be extended so that a suspended reminder is indicated there, on its own line with an appropriately descriptive text.  The "remove" and "modify" actions would be naturally applicable, and would cancel a suspended reminder or modify the time of it.  For the latter, the "before/after the event starts/end" drop-down control could be replaced with a static text saying "from now", otherwise reusing the existing relative time input UI.

2. The tooltip for events currently shows the reminders set for it.  A line could be added showing when a currently suspended reminder will be triggered.  Alternatively, the line for the reminder that has been suspended could be augmented by a text saying something like "(suspended until DD/MM/YYYY HH:MM)".