How can i add a custom field "select issue" but only the issues of an X project?

[Jonathan Lefebvre]

I'm creating a project to track my hardware expenses. The goal is to track from "To-Buy" until it reach "Reimburse by subsidies". And i have another project to track all my subsidies program from "Program"->"In review"->"Usable"->"Fully used". So i want a custom field into "Buying" project to select one of the issues of "Subsidies" project.

Bonus; Slecting only issues at "Usable" Stage.

Is it possible?

[Kian Stack Mumo Systems]

Jonathan, 

You can't create a custom field that contains a list of all other tickets in the system. The closest thing would be an issue link. Sadly you can't restrict this to a specific project unless the people creating the link do not have permissions to link to any project except to the "Subsities" one. 

As for prompting users to choose the issue at the usable stage, create a new screen with the "Linking Issues" field and attach that to the transition leading into "usable". 

The links below provide more information about each subject. 

https://confluence.atlassian.com/jirasoftwarecloud/linking-issues-776997756.html

https://confluence.atlassian.com/jirakb/mapping-a-screen-to-a-workflow-transition-720634253.html