Can't select both multi-city AND flex dates???
 

The option to select both seems to be present at the outset of building a 3city outbound, but by the time I get to entering the last (of the same three cities as on the outbound, but in reverse order) the flexible dates button is greyed out and cannot be selected, EVEN THOUGH INITIALLY IT WAS., and the "Search by price" button has been (automatically?) selected.
OTOH, in the process of creating the multi-city, there is a celandar for indicating flight dates, presumably to provide a basis around which flexible dates could be determined---otherwise, "flexible dates" could mean infinity, cleary NOT helpful.
So what am I/is .bomb missing?:confused:

Since the flexible date search is only two-dimensional, once you add a third leg, there's just no way to present it in that format. The site must assume any 3-leg multi-city is a triangle trip, even if you're only using it to force intermediate points.