Action - Trim whitespace

I'd like to have an action that is similar to a $trim(x) function that will remove leading and trailing whitespace (space characters) available to apply to different tag fields.

Is there's way to use $trim(x) function within action without manually editing any script files?

I don't understand. If you do not manually edit an action you don't get any changes.

Except the remove fields actions there is no action that allows a list of fields.

If you know which fields you want to trim, you can use an action of the type "Guess value" e.g. with
Source: $trim(%artist%)==$trim(%title%)==$trim(%album%)
Format string: %artist%==%title%==%album%