When creating a permission scheme from a scratch, it is needed to set a lot of permission allowances for different user types/groups.
It takes time to go through all the options adding the permission rules one by one.

Example:
You wish to grant 'create attachments' permission for the reporter, project lead, current assignee and 3 distinct groups.
This requires you to scroll down to the create attachment (or select it from the list on the 'Add New Permission' screen) on the 'edit permission scheme' click 'add' and then on the new screen select 'reporter' and click 'add'. After clicking 'add' the view is returned back to 'edit permission scheme' screen, scroll position being at top of the page (a minor annoyance, it could return to same scroll position as when the 'add' was clicked). Then you need to do the cycle again for adding the permission for project lead, current assignee and once for all the 3 groups.

Could it be possible to make an improvement, where you could use checkboxes (instead of radio buttons) in screen 'Permission Schemes' > 'Add New Permission' to be able to select multiple options at once.
Also changing the single select menus (atleast the group menu) into a multi select menus would be helpful.

(See the attachment)

I understand there already is a similar request, but I thought I could provide a bit more information by creating a new one.
JRA-1390 << The related issue