If you click on the projects button (green file folders) you will see the above image
Notice the blue Future tab, that is where you put projects that you don't want to be working on just yet.
If you close a project down to just the line (tree view not showing) you can hit CTRL-X to cut, and then click over on Future and hit CTRL-V to paste.
If you have the tree view showing, the paste functionality will not work and you will end up making a second copy of what ever project you had copied earlier.
As long as you have "Start" date enable on project view, any top level project (top level projects only) on the future tab will be moved to the projects tab on that date.
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