It has been documented that custom fields with global context can become a performance issue for JIRA, so the recommendation has been to limit each field just to the projects in which it is relevant.
As a Jira admin, it is difficult to manage the project contexts of a field in the current interface (as of version 7.10.2 at least). The multi-select list requires that you hold down CTRL when clicking a project in order to add it to the existing list rather than replacing the existing selections, and you can only see a few projects at a time so there is a lot of scrolling involved.
Please consider changing this to be like the interface when adding issue types to an issue type scheme – two boxes, left and right, and you move items from box to box in order to include or remove them.
Suggestion
Hi everyone,
Thanks for raising this issue and sharing your feedback.
We’ve revamped the entire UI of the context configuration page and introduced performance changes to prevent high load times for larger instances.
All these improvements are available in the recently released Jira 9.7 and later versions.
Check out our announcement post and for more details, head to Jira 9.7 release notes.
Artur Falborski,
Jira DC Software Engineer