kleimaj/multiSelect.js: 🍦 ✨ Simple multi-select pure vanilla Javascript library.

PhilippeMarcMeyer/vanillaSelectBox: A dropdown menu with lots of features that takes a select tag and transforms it into a single or multi-select menu with 1 or 2 levels

DashboardCode/BsMultiSelect: BsMultiselect is "multiselect input" plugin that reuses your Bootstrap 4 theme and doesn't bring its own css (unless you would like to add it).

snapappointments/bootstrap-select: The jQuery plugin that brings select elements into the 21st century with intuitive multiselection, searching, and much more.