This would also help a lot if you only vaguely care about time. For example, if I know one event happens on Tuesday, but I don't want to specify when on tuesday, and another event happens the next evening, there's no way to have the second event depend on the first, without giving the first one a fixed time. Dynamic specifications would be one way to allow for that.
I have developed kind of hacky workaround for this, until the hoped-for inclusion of this ability as a real feature. I first put down a series of linked events, day1, day2, etc. The first is positioned on the first day of the timeline, and each subsequent one depends on the previous. (This way I can insert a day later if I need some additional events.) Then I make events dependent on the day containers. An event at 2pm is dependent on the current day start + 14 hours. Something that happens "the next morning" is dependent on the next day start + 9 hours. That way if I change the start or length of the 2pm event, the next one stays anchored. Some fixup required when inserting days sometimes (does the 'next morning' event have to move to a new day?) but this is a lot less fiddly than counting hours between events to get their times right.