I would like to know if there is a way to make only level 1 categories visible on the gallery homepage. And to get to the level 2 category they have to click on the corresponding level 1 category .
There's a setting (AdminCP->Gallery->Modify Settings->Categorybit Options->Depth of Categories) to determine the depth that are shown. Look at my Gallery. It's set up the way you mention.
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Linear Mode
