You can create as many custom fields as you want with these types, others won’t be supported and will not appear in the templates.
summary description labels duedate priority environment components fixVersions versions resolution assignee com.pyxis.greenhopper.jira:gh-epic-label com.pyxis.greenhopper.jira:gh-epic-link com.pyxis.greenhopper.jira:gh-sprint com.atlassian.jira.plugin.system.customfieldtypes:textarea com.atlassian.jira.plugin.system.customfieldtypes:multicheckboxes com.atlassian.jira.plugin.system.customfieldtypes:float com.atlassian.jira.plugin.system.customfieldtypes:select com.atlassian.jira.plugin.system.customfieldtypes:labels com.atlassian.jira.plugin.system.customfieldtypes:radiobuttons com.atlassian.jira.plugin.system.customfieldtypes:multiselect com.atlassian.jira.plugin.system.customfieldtypes:cascadingselect com.atlassian.jira.plugin.system.customfieldtypes:textfield
Hidden fields in the Templates
attachment issuelinks com.playsql.requirementyogijira:rylinkcf