Show dotfiles/hidden files by default

Is there a way to display hidden files by default and not by pressing 'I' (for some reason my '.env' file is treated as a hidden file, while .gitignore as a 'dotfile')?

Hidden files (beginning with .) are shown by default: filters.dotfiles = false. H will toggle these.
See :help nvim-tree.filters.dotfiles

It sounds like your .env file is ignored by git - perhaps in your ~/.gitignore.