adding any code to functions.php is potentially problematic @fionavar. a lot of people do it, but I don’t want you to do something which actually is not “best practice”, hence the proposal to use “code snippets” which does not have those problems.
regarding catering for avada (or any other popular theme/ plugin); testing and using all plugins/ themes (esp. when commercial such as Avada) is something I simply can’t do and I don’t see a good reason for that either; AO is very flexible, with plenty of config options and even more filters which code can hook into, so almost any (and I’m being careful, I could just as well write “all”) problem can be fixed or worked around. that’s the power (but also the drawback) of using AO.
now to spill the beans; the next version of AO will probably have an option to disable AO for logged in users. but don’t tell anyone ??
have a nice weekend!
frank