How can I create a similar to Template Modification but instead modifies "Style Properties"?

[rdn]

So that updating style in the future is very easy.

 

[rdn]

Any how?

 

[Jeremy]

There is no such system in the software as it stands. You will have to accomplish this via an add-on.

However, you may be able to accomplish this by creating a template modification for the CSS directly (which translates to and from style properties).