Orbi RBR40

Sorry.  No Orbi router can act as a satellite.  The basic design doesn't allow it.  What you CAN do is connect it to an Orbi router using ethernet cable and run it as a separate system.  (No cable: no connection.)

• If you run it in the default router mode, it will create an entirely separate WiFi network, which may cause enormous problems.
  Every device connected to it will get an IP address in a different IP subnet and be essentially "unreachable" from the rest of the network.  There's just a lot to go wrong and be frustrating.  That is why....
• The recommendation is to wire the router and place it into Access Point (AP) mode.  That way, the primary Orbi will assign all IP addresses and control the network.  You can give this separate WiFi network the same SSID as the primary, or you can create another WiFi SSID for it.  The main issue is that devices will not "roam" between the two Orbi WiFi networks.  As far as the main Orbi is concerned, everything coming into it from the RBR40 is "wired", not WiFi.
• If there are devices which basically never move, such as computers, TV's, NAS boxes, thermostats, irrigation systems, garage door openers, (the list goes on and on), then the lack of roaming is immaterial.  For things like cell phones, tablets, and laptops there can be some frustration when the user forgets, "Aha.  I moved across the house and my service has fallen dramatically.  I need to disconnect from WiFi and reconnect."