It appears that the "Create Constrained Issue" problem logged here
SRJIRA-2926 was fixed in Jira 7.13.1 and broken again in Jira 8.
The "Create Constrained Issue" feature as described here no longer opens in a modal window and is opening a new tab with the create form instead.
I am not yet sure if it is the same problem as described in
Steps to reproduce:
1- Follow this guide here
2-For "What section should this go in" Choose operations-operations so it appears in the more menu
3- Try to use the new button
The expectation is to open in a modal window but instead, it opens in a new tab
impacts scriptrunner 5.4.49-jira8 to 184.108.40.206-jira8
Tested in Jira 7.13.1 on Scriptrunner 5.5.3 and it works