Lighting Window
https://docs.unity3d.com/Manual/GlobalIllumination.html
The controls of the Lighting window are divided among three tabs:
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The Scene tab settings apply to the overall Scene rather than individual GameObjects. These settings control lighting effects and also optimisation options.
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The Global maps tab shows all of the lightmap Asset files generated by the GI lighting process.
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The Object maps tab shows previews of GI lightmap textures (including shadow masks) for the currently selected GameObject.
The window also has an Auto Generate checkbox below the displayed content. If you tick this checkbox, Unity updates lightmap data as you edit the Scene. Note that the update usually takes a few seconds rather than happening instantaneously. If you leave the Auto Generate box unticked, the Generate Lighting button to the right of the checkbox becomes active; use this button to trigger lightmap updates when you need them. Use the Generate Lighting button if you want to clear the baked data from the Scene without clearing the GI Cache.