User By Permission allows the selection of one or many User(s) among a population of User granted to specified permissions

What is it?

This customfield allows to select a user depending on its Permission on the Issue (here users having the Browse Permissions) :

How to configure them ?

Create the Custom Field

When adding a new Custom Field, select the custom field Type User Picker By Permissions

Configure the Custom Field ...

You will have to configure your custom field in order ...

... to filter the User by their Permissions. 

The selection of the required Permission can be done in the following screen :

See also ...