Board Thread:Questions and Answers/@comment-29321837-20160727144607/@comment-856627-20170115230534

To clear up some things: only one Trigger in main and one in sub can be activated at a time, but exclusive optional triggers aren't limited by that since they add up to another trigger, which also means two Kogetsu+Senku and one Kogetsu+Shield is possible. You can see that here (question 167).

As for Chika not being able to use Lead Bullet and Bagworm at the same time, Ema said they can't be activated at the same time due to both necessarily taking the sub slot. Lead Bullet doesn't take the side slot to the trigger it combines with like exclusive optional triggers do, but I don't know if it was explained why that is, while the reason why Bagworm goes in the sub is obvious.