Under Admin, Advanced Settings, a Jira admin can change jira.text.field.character.limit from the default value of 32767
This applies to all multiline text field in that Jira instance.
For an individual field you could look at using a validator in the workflow or even a ScriptRunner behaviour (disclimer: I work at Adaptavist)
I don't believe that this feature is currently editable in Cloud
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.