XF 2.0 Inherit extra.less for child styles

I have created a new style based on default style and applied several changes in extra.less. When I create a new child style from this, the extra.less settings are not inherited. Is there a workaround without copy-pasting the parent extra.less to the child? I'd like to maintain only the extra.less from parent style and only change specific color settings for the child style if possible.
I found a way to do it. First I added a new template in the parent style called "custom.less". Here I placed all the common CSS/LESS customizations.

Then for each child style created from the parent style, I add in extra.less:

{{ include('custom.less') }}

//Any css code to override those defined in custom.less