As originally requested here, this mod provides buttons for users that regularly use the [ltr] and [rtl] tags, usually on forums that are multilingual and support languages such as Arabic.
It is compatible with all versions of SMF 2.0 from 2.0.1 onwards (it says 2.0.15 now, because that is the latest version of SMF 2.0, but the installation file will work with all future versions up to 2.0.99).
Install this modification through the package manager. It only edits three files, so nothing should go wrong.
1.1 - 21 September 2018 Update for 2.0.15 compatibility 1.1 - 26 October 2009 Update for 2.0 RC2 compatibility 1.0 - 14 August 2009 First release