Go to your home folder in the finder and press Shift+Cmd + . to see all hidden files. All you need is in

~/Library/Application Support/kstars

Here you find the folder gsc containing the GSC catalogue, folder darks and defectmaps containing any captured dark frame information, astrometry containing all the index files and analyze with the analyze files from your last sessions. Also your settings database in userdb.sqlite including a backup file from this (and you should store this file as a backup somewhere else to have another copy if you need it later). Don't remove other files from here unless you plan a reinstallation.

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