Jira's native JQL is not able to do this. JQL is designed to return Jira issues, it is not as adept at returning a substring of a field to a specific issue. That kind of function though seems like something that could be done with a SQL query.
As such, perhaps you can use a plugins such as SQL for Jira Driver: Convert JQL to SQL this plugin also has other related plugins that mightbe helpful here. For example the SQL for Jira - Custom Fields appears to allow you to use SQL formulas to populate custom fields in Jira. Perhaps with this you could use a SQL substring in order to create a new custom field that only contains the specific data you want to show in conjunction with that issue.
@Jobin Kuruvilla _Adaptavist_ Have anything to comment here please? The requirement is to perform substring operation on the custom multifield text value populated onto confluence from Jira.
This is not a generic JQL function requirement. You might want to write a custom searcher for your custom field or write a JQL function in a plugin that does what you want.
But features like displaying only last X digits are beyond the search functionality. That will be a modification to the custom field implementation!
