what is the shortcut to build directly 4 mass storage around on mass extractor ?

sometime when I want to assist a mass extractor that is upgraded from T1 to T2, instead of help the mass extractor, my engineer build automatically 4 mass storage around it.

how is it possible ?

This is added by FAF as a convenience to make it easier for players to put mass storages around T2 extractors. It helps us to make the storages without needing to use a template.

If you select an engineer with no orders, and right-click on a mex that is upgrading from t1 to t2, the engineer will get an order to assist the upgrade.

If you hold shift and right-click on that mex again, the engineer will get additional orders: it will get orders to build the 4 mass storages around that mex. Or at least, as many of the 4 mass storages that can fit, if they're not blocked by buildings or terrain.

So this is happening because you are clicking twice.

Great thank !