When mouse-over construction is enabled via the shortcut button or hotkey (default Shift + Y), the following features are available for entities within your reach range:

Construction

Ghosts within range will be automatically revived if you have the proper materials in your inventory.

Upgrading

Entities within range that are marked for upgrade will be automatically upgraded if you have the proper materials in your inventory.

Repairing

Entities within range that have less than full health will be automatically repaired if you are holding a repair pack.

Deconstruction

Entities within range that are marked for deconstruction will be automatically mined.