GitHub - snapappointments/bootstrap-select: The jQuery plugin that brings select elements into the 21st century with intuitive multiselection, searching, and much more.
Bootstrap Search Examples
A Bootstrap / jQuery based select box with search and multi-select options
Keyboard tab navigation to search field of material select i - Material Design for Bootstrap
Searchable Single & Multiple Select Plugin For Bootstrap 4 | CSS Script
8 Bootstrap Multiselect Boxes - csshint - A designer hub