For “mode,” use {lo’} “use” (noun).  “Night mode” would be {ram lo’} “night use, night usage.”  “Search mode” could be {SammeH lo’}.  ({nejmeH lo’} also works; depends on how confident you are in your search engine apparently.) “Lesson mode” could be {ghojmeH mIw lo’}.

For “theme,” {tu’qom} “appearance, configuration” should work.  

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