i checked it out, and it seems that you need to accept the Steam Workshop Agreement before you can set your workshop page to Visible! i should've accounted for this in the game's UI, very sorry!!
you can do it here: https://psteamcommunity.yuanyoumao.com/sharedfiles/workshoplegalagreement
after accepting it you should be able to set visibility to Visible
i'll soon update the game to notify the user whenever this happens, thanks!!

as a side note, the visibility selection isn't currently synced w/ the workshop, so it gets reset to Unlisted when reloading the game/map pack (this will get fixed before editor releases!) - but not the actual visibility!