Is it possible to mechanically tie two footprints, so that they would be moved as a single unit? The background of my question is that there are cases, when a component is broken up into two parts which have a very well defined mechanical relationship, but that’s not apparent in the schematic/layout.
E.g., the sockets of SFP+ connectors have an associated cage that’s got to be aligned with the connector.
What is the canonical way of working with such cases in KiCAD?
So in this circumstance I think when defining the footprints I’d pay special attention to the location of the origin for both footprints so that when in the correct position relative to each other their origins coincide.
This will make for quick and precise positioning during PCB layout, then they can be grouped so they don’t inadvertently get separated.
If the schematic has only one symbol, I make a single footprint for both components.
If there are two symbols in the schematic, I group both footprints.
There is at least another case. A single heatsink, for example, with 2 power MOS and a diode. The relative positions may change during the development of the layout. The heatsink may or may not be present in the schematic.
Connectors which can be snapped together are an example of a use case like this.
I remember there is an old (probably still open) issue on gitlab for creating extra snap points in footprints to ease the alignment. You could search for that and give it an upvote.
But most often such footprints will have a well defined and known pitch. So set the grid to that pitch and drag them around for the alignment, and then group them as greg_m already wrote.