@shabiu With different models than yours, it worked only if the "second" mesh (M5 in your case) is set with an operation mode = Access Point.

  @yves_b thanks. works well

devices connected to the M5 I can see users there but don't see them on the main network

as a result, I lost the parental control to devices connected to M5

  @shabiu 

I think you can do that, but might need to set everything carefully. Below steps assume your Main Deco XE70PRO connects to ISP modem/router using Dynamic IP configuration (default).

1. Delete M5 from Deco mesh in Deco app, if it is configured there;

2. Power off all XE70PRO;

3. Unplug Main Deco XE70PRO from its Ethernet cable and connect M5 to it;

4. Power on M5. Create NEW Deco mesh network in Deco app with M5 as Main Deco. I think it should have different SSID from XE70PRO to have that done;

5. After you configured M5 as Main Deco of new Deco network, power off M5, unplug it from Ethernet cable, plug Main Deco XE70PRO back and power on all XE70PRO;

6. Connect M5 with Ethernet cable to Main or any Satellite Deco XE70PRO, or directly to ISP modem/router. Power on M5.

You should now have two Deco mesh networks at your place.