Well, ironically, while this is a common question these days, there is no way to toggle building in a match while it is disabled. You will simply see the little icon that it is unavailable. That said, in a scenario where the building feature is back in the game, here’s how you do it. It comes down to the platform of choice that you are on. For example on consoles, you can press the B/circle button on controller to open up the building menu. It is as simple as that. Pressing the button again will switch you back to normal fighting and inventory options. As for how to toggle on building mode in the future when we might have both the build and no build game modes, that is a different story. More than likely, there will be set modes that you can pick in the lobby that have build and no build names for them. You pick the one that you prefer and then hop into that mode.