Create a template from customized JIRA issue with sub-tasks

[Kevin250]

I have a project in JIRA that I've customized quite a lot, with three custom issue types, and around 15-20 custom sub-task types. Each issue type and sub-task has it's own custom fields, meaning that I have a separate set of screens for each issue type and sub-task. This took me a lot of time to set it up as I've wanted, but it's working as it should. Now, I've have created a "template" issue of one of those desired issue types, and added desired sub-task types. In practice, it should mimick our onboarding process, with 10 or so sub-task types for different departments.

Clone Issue option works, but it will require a user to go to this "template" issue (to remember the URL / issue number), click Clone Issue and then input into field types the desired values.

I've tried the following plugins for making templates out of this "template" issue, but the results disappointed me:
Issue Templates for Jira - creates a new project just for Templates, and requires that I again customize the entire issue I have in my desired project into this one. As I tried to do that, I had issues with custom fields in subtasks, as the template was constantly mixing the fields per subtask for some reason in this newly created project for Templates. Also, when I've uninstalled the plugin, I had issues with creating new issues in my desired project, since the plugin adds an additional function in the workflow transition for creating issues, so I had to debug that one as well ..
Easy Templates for Jira Issues - doesn't support more than 10 sub-tasks in JIRA Server installations when you create a template from your issue :) Contacted their support, this bug is not on their roadmap to fix
Smart Issue Templates for Jira - in this plugin, you need to create what they call a "Hieararchy" of issues, and it just doesn't work, no matter which sub-task type you pick as a "child" in the hieararchy, it's not allowing you to change the type of that sub-task, and it's locked to the first sub-task type you have defined for the project. Also, another bug is that even if you try to create a hieararchy, it never gets created, and just throws exceptions in log.

So, my question for this one is, do you know a plugin that will allow me easily to create a template from already created issues with sub-tasks (both filled with custom fields), which will allow users to customize fields in the issue when they decide to use that template? If nothing works, in the end I'll resort to using Clone Issue button / function, but hopefully there is something more useful than this.

For the reference, I am using Jira Server 7.9.2, local installation

https://19216881.org/ https://1921681001.link/ https://19216801.digital/