I have 1 ISP. The Mikrotik router is connected to that ISP in ether1 (192.168.0.3). Mikrotik gives out DHCP addresses 10.0.0.0/8. My PC is connected to it (10.0.0.6). The other network has a router(ddwrt) that connects to the mikrotik router and gives out 10.1.1.1/8 addresses

I want network 10.0.0.x to be able to connect with network 10.1.1.x, specifically my PC to monitor other computers on the other network. How can I proceed of this? Thank you so much!

https://i.stack.imgur.com/Q3k6L.png

Why have the other router ddwrt getting in the way. If you have a wired connection, then the ddrwrt can be used solely as a switch and have one network.
Since its setup as router, then you have no access to devices behind it.

10.1.1.1/8 is not a valid subnet.

Anyway, you need to either add a static route to your ddwrt's network via it's address in mikrotik's network.
And on ddwrt router disable nat and allow such connections in firewall.

Or alternatively you can establish port forwarding on ddwrt router, just as you would do for outside access in "regular" case, where it is connected to ISP network directly.

Since its setup as router, then you have no access to devices behind it.

NAT, firewall and lack of routes is the reason, not the fact that device is acting as a router.
It's a completely legit setup, just needs proper configuration.

10.1.1.0/8 is part of the same subnet as 10.0.0.0/8, so your client device, i.e. 10.0.0.6 will never send the packet to the gateway, does not matter what NAT, routes etc you have on either router

is it all your private network? looks like you have a triple NAT going on.

If i were you i would see if i could get my global ip on the mikrotik instead of the 192.

make your mikrotik have a masquerade (it already should with your current set up, and change your mikrotik network to something smaller. say 10.0.0.0/24.

on your ddwrt make the subnet 10.0.1.0/24. remove the NAT or port forward to allow your pc on the mikrotik network To have access.

use static or a dynamic routing protocol to connect the two routers together

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