Keep projectlist in focus
In todoist.com if a project contains many tasks the user has to either use the dropdown on the task to move the task to a project or move the task further up the list and then move it to a project. If the project list stayed stationary while scrolling down on the task list it would be easier to assign tasks to projects.
This would be useful when the inbox gets long and you would like to start sorting the inbox from the bottom up instead of top to bottom.
This would also mimic the behaviour that is in outher popular webapps like gmail where the left pane stays in place while scrolling down.