Why the project drop-down field is inactive on an activity details page? How can I move activity to different project?

General Questions
 
Q: Why the project drop-down field is inactive on an activity details page? How can I activate it?:




A: The field is inactive due to the lack of user permissions.

The role permissions for the user required for this functionality are:


In the "Global permissions" section:

"Access all projects":
 

In the "Permissions for projects where user is NOT a member" section: 
 
Activities - "View all", "Add", "Edit all", "Delete all";
 
Time entries - "View all", "Add for someone else", "Delete all";
 
Project - "Edit";
 
Members & assignees - "View and manage":





Once the above permissions are enabled, the project drop-down list will get active: