For the examples of Native American Heritage Day and USA Election Day, it seems like the individual steps to find the dates are already available in LuxCal, but they just need to be iterated together such as in the examples below.
Native American Heritage Day:
1. find the fourth Thursday of November
2. then add one day
3. repeat each year
Last Day of Maryland Voter Registration:
1. find the first Monday of November
2. find the first Tuesday after step 1
3. find the date that is 21 days before step 2
4. repeat once every 2 years (or apply step 1 as every other November)
Whereas events that depend on other events would agreeably be more difficult, since then a particular event or event series would have to be selected, and changing or deleting one event would cause changes or errors in the events dependent on it.
For complicated formulae, perhaps an option to select dates programmatically might be needed, such as:
FourthThursday( EveryNovember ), +1*Day
FirstMonday( EveryNovember/2 ), +FirstTuesday, -21*Day