Importing issues via .CSV there is no field Issue Key

[Troy Wilson]

I have a project created through .csv and looking to run externally, then import the updated issue in bulk form the .csv file.

The issue I am having is I aim to import the file a second time (first being project creation), when I do it no longer allows the field for Issue Key which is used on the initial import, and seeing as the link to this Issue Key is not there, it is creating duplicate issues as opposed to updating the existing issues. I beleive this is what it shoudl do based on the article:
https://support.atlassian.com/jira-cloud-administration/docs/import-data-from-a-csv-file/

Also of note, Start Date is no longer there, so the new issues miss that also, it seems wierd that on creation there are all fields, but on update there is a limited number of fields that can be added.

[Troy Wilson]

Probably not having start dates and other fields missing is significantly more important than simply the key, because what I can do is delete the tasks in bulk and import tasks from the .csv againm, say as a workaround.
However, if I can't import all of those fields (key, start time etc.), I'd probably need to create a new project every time I want to import tasks as the current workaround, and that would be immensely irritating for my IT / Admin.