This object is part of a locked union. Continue?

 click on image to view

This message occurs while trying to move a union if primitives are locked in footprints in the union.

To avoid this popup all primitives in the footprints in the union need to be unlocked in each footprint library.

That's it !

PCB Filter - Find Traces with Exposed Copper on Outer Layers

((ObjectKind = 'Track') or (ObjectKind = 'Arc')) And (SolderMaskExpansionMode = 'Manual') and OnOutside

That's it !

EXTREME Copper - Up to 200 oz

Heavy Copper and EXTREME Copper PCB Design for Maximum Reliability

Figure 1. Sample featuring 2oz, 10oz, 20oz, and 30oz copper features on the same layer.

Source: https://www.epectec.com/

Related Altium Link : Metal Core PCB Design and Manufacturing Guidelines

That's Heavy !

Place Multiple Footprints - Tricks

Open a PcbLib library and a blank PCB. 

Place a track in the PCB, then select and copy the track.

The library paste should work after that.

Select all or multiple parts in the PCB Library panel, then copy, then paste into the PCB. 

Open the PCB list and copy the footprint and height columns and paste into a spreadsheet.

Reference: PCB Library parameter list? - Altium Discussion Forums

That's it !

Place Multiple Components in a Schematic

See these links on the Altium Forum.

Bug, regression, cannot paste from schlib - Altium Discussion Forums

Mass component import into schematic - Altium Discussion Forums

Michael shared a useful workaround for placing multiple components.

That's it !