Summary

Space templates cannot be used from another space when creating a page.

Currently when creating a page from template with "Use" button, the page will be created on the space from where the template is located.
An alternative is to create the page directly from the space, and then select the template on the right panel. See Create a page from a template for steps on how to do it. This is only possible if user have add page permission from the source space.

Suggestion

A suggestion to enable users to create pages using templates from other spaces would be to allow them to select the templates when they have view permission on the source space.

The user is already able to select the template from another space when having add page permission. With this enhancement, customer would not need to create global templates, and would also avoid having duplicate templates in different spaces.