I guess you could start by using the duplicate option in table edit mode. This will ask you what fields you want to duplicate to the new table all or some by ticking field names. once you have the second table, then you can think about adding a table reference to link the 2 tables. that add scripting to fill data into the linked tables/fields.

see also the excellent videos on how to add the table references etc.

Allstar- see here for lots of videos !!!

https://www.youtube.com/@NinoxLearning/videos

 but re relationships specifically look at......

300.01 https://www.youtube.com/watch?v=T5EJL7u4wlk

300.02 https://www.youtube.com/watch?v=Iw18BMWSEyY

300.03 https://www.youtube.com/watch?v=xI5SA3Vbx7A

https://www.youtube.com/watch?v=ZgZODeJed3w

Allstar Scores said:
Then I want to be able to share these smaller tables, so people will only see their group.

May I recommend you look into something called dashboards. You can watch the following videos:

Nioxus

Ninox

The idea is not to change the basics of DB structure to account for user error or security. You can now create dashboards to take control of the entire UI for users. I use dashboards all the time and I'm the only user of my DB, trying to keep myself from doing stupid things. :)

There are lots of videos on YouTube. Another option is to get a membership with Nioxus for a few months. You can watch all of their training videos on dashboard, security, etc, so you can get up to speed on designing your DB to your desire. I found their training videos very helpful when I started in Ninox.

Hi Allstar Fred is right here. Also, you can create user roles and then scope what records that user is allowed to see, and give them editing rights or not.