First, it's important to know that MoCA and DOCSIS are two completely separate technologies designed to communicate on completely separate frequency bands over the same 75 ohm Cable TV-style coaxial cables, so they coexist with interfering with each other or even being able to talk to each other directly or even know of each other's presence. The signals sent by your MoCA adapter cannot be received by a DOCSIS cable modem and vice-versa. (There are some DOCSIS routers with built-in MoCA support, but it's not standard.)

A 5G "modem" with an Ethernet port that could be connected to an Ethernet-MoCA adapter like you show in your diagram, is probably more than a modem. It's probably also what we'd call a "home gateway router", which means it can act as a NAT gateway and DHCP server. So you probably don't need to have your old DOCSIS "modem" (really a home gateway router) on your network at all anymore since your 5G modem/gateway device serves those roles. You could replace it in your diagram with a second MoCA-Ethernet adapter, and a small Ethernet switch if you need more Ethernet LAN ports. If the DOCSIS router you already have happens to include MoCA support, you might be able to repurpose it to just be a transparent MoCA to Ethernet adapter with built-in 4-port LAN switch, by disabling its DHCP Server feature, and disabling (or just ignoring) its NAT and DOCSIS features.

First, it's important to know that MoCA and DOCSIS are two completely separate technologies designed to communicate on completely separate frequency bands over the same 75 ohm Cable TV-style coaxial cables, so they coexist on the same household Cable TV wiring without interfering with each other, without even being able to talk to each other directly, and without even being able to detect each other's presence. The signals sent by your MoCA adapter cannot be received by a DOCSIS cable modem and vice-versa. (There are some DOCSIS routers with built-in MoCA support, but it's not standard.)

A 5G "modem" with an Ethernet port that could be connected to an Ethernet-MoCA adapter like you show in your diagram, is probably more than a modem. It's probably also what we'd call a "home gateway router", which means it can act as a NAT gateway and DHCP server. So you probably don't need to have your old DOCSIS router on your network at all anymore since your 5G modem/gateway device serves those roles. You could replace it in your diagram with a second MoCA-Ethernet adapter, plus a small Ethernet switch if you need more Ethernet LAN ports. If the DOCSIS router you already have happens to include MoCA support, you might be able to repurpose it to just be a transparent MoCA to Ethernet adapter with built-in 4-port LAN switch, by disabling its DHCP Server feature, and disabling (or just ignoring) its NAT and DOCSIS features.