This is where the rule of avoiding bloat applies best. You should ask yourself why is it that you have so many errors generated with the code you use. In theory you should not fix the errors but wait for the author to fix it as if you fix it yourself you basically forking the plugin/theme.
More specific to your question, the answer is that it is probably impossible to have it right better than 90%. You can use the “query monitor” plugin to get stack trace, but even stack trace will have only limited value for non trivial situation. For example you might get an “undefined index” type of error when accessing an array element which is a result of DB access bug that happens when a value is being saved, and which you see the symptoms of it only when it is used.
And since finding and fixing non trivial errors is not trivial, and having errors is always a possible gateway to security breaches or general site malfunctions, you should just not use plugins and themes that leave you figuring this kind of things alone by not having timely updates or good effective support.