Hi,
we've come across an issue where people haven't been opening tickets during incidents, and have not been closing them when resolved.
I'd like to fix these and add the missing data. But I am unable to amend the created / resolved dates.
I have tried the import external method described here
When I get to the screen to map the fields some of the system fields are not there see for example Issue Key. There is no system field for it. Only a custom field.

Has something changed since the article was written?
Can anyone offer any advice on what can be done for me to be able to fix this?
Thanks