I made Related Items links for many different items using the Ctrl+R Related Items dialog.  In that dialog, I used the Grid dropdown to specify the Grid to be searched, entered a search string in the search box, then clicked the checkbox for the item to be linked to.  The Related Items links were created and appeared in each item's Related Items section in the Properties Pane.  But then I discovered that for some of these links, clicking the link had no effect.  Right-clicking the Item and then clicking "Show Item" had no effect.  I found that this happened when the item shown in the Related Items section had no home grid, for example, when the value shown in the Properties Pane > Basic > Home was either empty or Scratch.  It seems that clicking an item in the Related Items section should take you to that item in some grid.  Perhaps to the grid that was used to find the item in the Related Items dialog.  Or perhaps a dialog should pop up saying "Related Item has no Home Grid.  Select a Home Grid for this Item: <dropdown box showing grids>".

It took me a little while to figure this out and find out how to set a home grid for an item that doesn't have one.  It doesn't seem that there is yet a section in the manual specifically explaining the Home Grid and its various uses, or maybe I didn't do a good enough search.  If there isn't such a section, that would be good to have eventually.  Many thanks as always.