On the left-hand side of the Light-O-Rama Sequence Editor is a Tools panel, with three subpanels ("Saved Tools", "Recent Tools", and "Clipboards"):
The Tools Panel
You can hide or show any individual subpanel by clicking on the arrows at its top right. For example, with the "Recent Tools" subpanel hidden:
The Tools Panel, with the Recent Tools subpanel hidden
The entire Tools Panel can be hidden by clicking on the pin in its top right. This will cause the Tools Panel to collapse down to a narrow bar on the left, with a wrench icon on a tab:
The Tools Panel, hidden
Moving your mouse over that tab will cause the panel to be shown again, at which time you can use its various items. After you are done with it, and move your mouse away from the panel, it will collapse back down to be hidden again. If you instead want it to remain open, you can click on its pin icon again.
Whether the panel is collapsed or open, and whether its individual subpanels are, is remembered in between runs of the Sequence Editor - that is, they will start up in the same states that they were in when you last used the Sequence Editor.
For details on the subpanels, please see their individual sections of the help file: