Correct way to define alias interface br-lan:1

What is the correct way to define an alias interface in OpenWrt 19?
To date I have been using manual scripts that set them up using

ifconfig br-lan:50 netmask up

and all is good, however I was wondering if OpenWrt 19 /etc/config/network has options to create them as I have not found one yet.

I am asking specifically for OpenWrt 19 as I have a Linksys WRT32x that has lots of issues with newer OpenWrt versions and thus I cannot upgrade.

that adds an ip to the interface by using @lan for example.

What I want to achieve is to create interfaces with the colon notation like br-lan:10 for example.