Without any plugins:
You just need to enable highlight: (Idea v.2016, 2017 and 2018, previous versions may have same or similar settings)
File -> Settings -> Editor -> Inspections -> Java -> Serialization issues -> Serializable class without ‘serialVersionUID’ – set flag and click ‘OK’.
(For Macs, Settings is under IntelliJ IDEA -> Preferences…)
For Idea v. 2022.1 (Community and Ultimate) it’s on:
File -> Settings -> Editor -> Inspections -> JVM Languages -> Serializable class without ‘serialVersionUID’ – set flag and click ‘OK’
Now, if your class implements Serializable, you will see highlight and alt+Enter on class name will ask you to generate private static final long serialVersionUID.
UPD: a faster way to find this setting – you might use hotkey Ctrl+Shift+A (find action), type Serializable class without 'serialVersionUID' – the first is the one.