After typing Enter, before entering “paragraph 2”, press Bksp. This will erase the item number, keeping all other formatting attributes unchanged.
To suppress numbering in existing items, put the cursor at the very beginning of the item and press Bksp.
Note that such unnumbered item is still a member of the list. To get a “standard” paragraph, not member of any list, you must remove explicitly the numbering by toggling it either with shortcut F12 or pressing the toolbar button.
Note also that direct list numbering (as opposed to one provided by a duly configured paragraph style) is quite “sticky”, even if you assign another paragraph style. To get rid of numbering, see the preceding suggestion.
PS: always mention OS name and LO version as there are subtle differences between platforms and releases.