Just copy the the [Sh] section from the code below into your snippets file, e.g. in ~/.config/geany/snippets.conf.
[Sh] if=if [ %cursor% ]; then\n\t%cursor%\nfi for=for i in `%cursor%`;\ndo\n\t%cursor%\ndone else=else\n\t%cursor% case=case %cursor% in \n\t%cursor%)\n\t\t%cursor%\n\t\t;;\n\t%cursor%)\n\t\t%cursor%\n\t\t;;\n\t*)\n\t\t%cursor%\n\t\t;;\nesac\n%cursor%
[Sh] head=#!/bin/sh\n# -*- coding: utf-8 -*-\n# vim:fileencoding=utf-8\n# Created by {developer}\n# <{mail}>\n# DESCRIPTION\n# Version {date} hashpling=#!/bin/sh\n bashhashpling=#!/bin/bash\n cshhashpling=#!/bin/csh\n envhashpling=#!/usr/bin/env INTERPRETER\n utf8=# -*- coding: utf-8 -*-\n# vim:fileencoding=utf-8\n bash=#!/bin/bash rmdir=rm -vrd --one-file-system /PATH/* softlink=ln -vs -t /DESTINATION/PATH /LINK/FILE