Basically all possibilities for code-navigation are supported for named templates, variables and parameters. For example: Goto Declaration, Find Usages, Highlight Usages in File, Quick Definition Lookup, etc.
Find Usages works for Variables and Parameters as well as named XSLT Templates. It finds all places of a certain template in all XSLT Stylesheets that are contained in the specified scope.
The plugin also supports WebStorm Goto Symbol action. The names of templates, top-level variables and parameters are offered for that action to be able to quickly navigate to them by their name.