Linker
Mass Edit allows you to link placeable together thus keeping them together at relatively positions to one another whenever you move or rotate them.
Linking is done through a Linker Menu from which you can manage links by creating new ones, connecting placeables to them, removing them, and changing link types.
Currently the menu can only be accessed via the Open Linker Menu keybinding which is set to Shift+Q by default.
If the menu is opened without any selected placeables, then the menu will display all links preset on the current scene.
If you do have placeables selected, only links for those placeables will be shown.
A link node is created via a Dobule-Click on any empty point within the window.
Placeable can then be attached by selected them and pressing the Attach Selected to Link control in the left pane.