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Go to Settings | Issues
In the left menu, select Custom fields.
Locate the field you want. Click the … on the far right, and select Associate to Screens.
Select the “Default Issue Screen” for the project
Scroll to the bottom of the list and click Update.
Team-managed project
Team-managed projects don’t have a screen scheme, fields can be added to each issue type directly go by going to Project Settings → Issue Types, choose choosing issue type, drag dragging and drop dropping fields on the right panel to the fields list to add or create a new field
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