Custom help icon (?) for custom fields to display its legend

I have a custom field called ‘Complexity’ which is a drop down type. I will display 4 values namely, 1-highly complex, 2-mid complex, 3-low complex, 4-Not complex. I am currently displaying the legend for these values below my custom field in the create issue screen, but this takes more space in the screen. So I want to have a help icon (like ? ) next to my custom field, so that users will click that and read about the complexity hierarchy before selecting it. I know this is available for system fields like severity. So please help me to create one for my custom field.


I use HTML to append an icon to the right-side of the field. If the user clicks on this, I show/hide text in the description.
This is basic javascript and should not be difficult… But it’s ONLY avaliable in Server/Self-Hosted JIRA instances: JIRA Cloud doesn’t let you define arbitrary HTML.