Hi! Milestones' built-in Armoured Biters addon checks the mod name ArmouredBiters, so it doesn't show up with this fork, and the author is removing those built-in presets anyway: mods are expected to provide their own.

A control.lua with this is enough:

remote.add_interface(script.mod_name, {
    milestones_preset_addons = function()
        return {
            ["Armoured Biters"] = {
                required_mods = {script.mod_name},
                forbidden_mods = {"SeaBlock"},
                milestones = {
                    {type="group", name="Kills"},
                    {type="kill", name="behemoth-armoured-biter", quantity=1},
                    {type="kill", name="leviathan-armoured-biter", quantity=1},
                }
            }
        }
    end
})

Thanks, added in 2.0.7. As I understand it, on an existing save, press Reset in Milestones' settings to pick it up.