Deprecation of Subqueries feature
From October 2023, the Subqueries feature is no longer available in JQL Search Extensions. This change affects customers with saved JQL subqueries who installed the app prior tobeforeApril 2021.
The 6-month deprecation plan was communicated to these customers with recommendations to convert any subqueries through Extended Search before the feature was deprecated. Extended Search provides an equivalent function for every subquery JQL keyword with better performance and reliability.
...
The big difference is that you can use the nested query “component=UI” directly in your main query and without the need to create and index a subquery first. You can even narrow down you your query further:
issue in epicsOfChildrenInQuery("component=UI") and project in (ACME, SP)
...