It's an old bug ... but still annoying: Before Photoshop 2015.5 Generator exported only visible layers. Since 2015.5 all layers are exported, that leads to complexity, unwanted files and unnecessary work. Adobe planned to fix this bug (internal bug number is PS-3724) in spring 2017, but it seems their mind has changed ... So, please Adobe, fix it in spring 2019. Dear readers, please like this post, maybe it helps.