Normally, the user is able to use both Macro Buttons simultaneously, however, there are 2 cases when he/she is not:
1. Both Macro Buttons have the same stock button input. The functionality allows the user to have the same button assigned to both Macro Buttons. Both Macro Buttons can be configured differently as well (sub-mode, timing). If the user presses the Macro Button while the other one is being active and performing a cycle, then the modchip won’t accept the second input. If you choose to configure both Macro Buttons with the same stock button, make sure you use them in order, not simultaneously.
2. One configured stock button cancels the other one’s input. There is a button hierarchy that makes the game setting to determine what button is more important than the other and can be overwritten. If that’s the case, you can either use the Macro Buttons in order, one by one, or make a trade-off for a different stock button assignment.