Look for the issue keys of different issues included in the description of the current issue and link them with a specific issue link type.
Add the Update or copy field values to the transition of your choice.
Choose Current issue
Choose the Temporary text 1
Choose Set field value manually
Add the following expression in Advanced text mode.
toString(findPattern(%{issue.description}, "[A-Z]{2,}-[0-9]+"))
Add the Create issue link post function to the same transition after the Update or copy field values post function.
Select the issue link type that should link the main issue with the issues mentioned in the description.
Select Current issue
Select Issue keys in issue list
Choose Temporary text 1
Create issue link