After updating the emoji font in an older macOS, is there a way to visually find and insert newer emoji that the system emoji picker doesn't support?
All Emoji should show up when you use the expanded version of the Character Viewer. If you don't see Emoji on the list at the left, click on the gear wheel and then Customize to add it. You may also need to add the Unicode category and go to the range where the new Emoji are located (probably 1f300-1f900).