vimが終了せずにファイルを閉じることはできますか？

それです:bd。:help :bdvim 8.2 では以下を提供します。

:[N]bd[elete][!]                        *:bd* *:bdel* *:bdelete* *E516*
:bd[elete][!] [N]
            Unload buffer [N] (default: current buffer) and delete it from
            the buffer list.  If the buffer was changed, this fails,
            unless when [!] is specified, in which case changes are lost.
            The file remains unaffected.  Any windows for this buffer are
            closed.  If buffer [N] is the current buffer, another buffer
            will be displayed instead.  This is the most recent entry in
            the jump list that points into a loaded buffer.
            Actually, the buffer isn't completely deleted, it is removed
            from the buffer list |unlisted-buffer| and option values,
            variables and mappings/abbreviations for the buffer are
            cleared. Examples:
                :.,$-bdelete    " delete buffers from the current one to
                                " last but one
                :%bdelete       " delete all buffers