Short answer: you can’t change a field type (ie. from Text to Single Select), you have to create a new field and transfer data from one field to the next.
In our scenario, we had a field type of checkbox and only had one option: ‘Yes’. If it wasn’t selected, then we didn’t need that option added for a client.
Over time, we found that it would be better to have a definitive answer from the account manager on whether the option was needed or not. We needed a Single Select list of: No, Yes, TBD (‘none’ is added automatically by Jira and displays in first position).
First we used the Botron (now AppFire) app of Power Admin to tell us which screens, filters, projects this field would affect if we updated it.
Then we updated the field name with a suffix of DELETE which would change the name anywhere it was referenced.
Then we created the new Custom Field as a Single Select with the aforementioned values -and- as part of that Custom Field creation process, we were prompted to select the screens where it should appear. (Remember, up above where we found all of the screens that would be affected in Power Admin?)
Note: The new field always get added to the bottom of the screen.
We also had to determine the Projects and Issuetypes in which the new field could be found/used (we try not to use Global config) by selecting Configure to the right of the Custom Field to display the “Modify configuration scheme context” page. On this page, we selected the Issuetypes and Projects allowed.
Then we used the Tools > Bulk Change process to update the new field with the old field values. (that’s for another post)
Then we removed the old field from any screens and filters and and moved the new field up to the correct position in the screen.
After a few weeks, we will delete the old field from production and test.
Oh – and – yes, we did replicate the updates in our dev Jira environment, AND we documented this process with screen shots in the Jira Task that was assigned to me to carry out this endeavor.
Document! Document! Document!
FYI – no Confluence yet, but we submitted a request to Finance. Woot!
Here are the different field types a custom field can have: https://confluence.atlassian.com/jirakb/list-of-supported-custom-fields-for-request-types-in-jira-service-desk-customer-portals-867182673.html