As I understand it, conditional cases will only run if their conditions are true (putting if/else branches aside for a moment). This is probably the wrong terminology, but I'm calling cases without conditions 'unconditional'. These are the ones you get to choose manually in the prototype if you don't want (or can't) write the logic as conditions.

Is there a way to combine the two? What I really want to be able to do is click a button in the prototype, choose one of two cases, but then evaluate a condition and have an else block as well. So the there would potentially be four cases:

1. User chooses option one and condition evaluates to true.
2. User chooses option one and condition evaluates to false.
3. User chooses option two and condition evaluates to true.
4. User chooses option two and condition evaluates to false.

As far as I can tell, if any conditional cases exists, they override the unconditional ones and no popup is displayed.

You can have multiple cases on an event execute if you create multiple "IF" blocks. You can change an "ELSE IF" to an "IF" by right clicking on a case and selecting "Change to IF". So you can create interactions like:

If option one equals A, go here
Else If option one equals B, go there
If option two equals C, do this
Else If option two equals D, do that

However, there isn't a way to have some conditional cases and some unconditional cases in the same event.