I am trying to write a script to test a project we are working on.

Lets say i have a :for e from 1 to 10 do ={
: log message="hello"&e
}

basically what I want to happen is in the logs it must look like this
hello1
hello2
hello3
ect.

This i want to adapt to connection marking in the firewall mangle rules.

Try:
:for i from 1 to 10 do {
/ip firewall mangle add src-address=("192.168.0." . $i . "/32") ...
}