When searching through large schemas for element names, the search can take long. In 12.1.3, the search does not have a cancel option. This has been added in 12.2.1.

If the search is taking too long, the tree size can be truncated by reducing the Expansion Depth for the trees in preferences. Go to Tools > Preferences. Select XSL Maps from the navigator. Click the Show Advanced Options button and change the Expansion Depth for the XML Schema Maximum Expansion Depth option to a much smaller value. For trees that have hundreds of children at a single level, this value needs to be around 10 levels. This will mean that the search will not go below the level set here, but some trees can contain millions of nodes and the search can take long in that event.