Welcome! This forum has a treasure trove of great info – Scouters helping Scouters! Just a heads up, though - all content, information, and opinions shared on this forum are those of the author, not the BSA.
This may already be possible, but when I add new parents into Scoutbook for existing scouts, I have to go into each event and add that parent also [otherwise they have proven they don’t receive the meeting notices]. I seem to find that Scoutbook defaults to adding all the Scouts but not the Parents.
Use the Feature Assistant Extension to add multiple individuals to multiple events. After adding new people, I cycle through the “Add inviters” link that Feature Assistant Extension includes, using Select All to select the events, for example all the Pack meetings, and Select All to select all the youth, adults, etc. Just today it saved my hours!