gtk-builder-tool [COMMAND] [OPTION...] FILE
You should always test the modified .ui files produced by gtk-builder-tool before using them in production.
Validates the .ui file and report errors to stderr.
Simplifies the .ui file by removing properties that are set to their default values and write the resulting XML to stdout, or back to the input file.
Lists all the named objects that are created in the .ui file.
Preview the .ui file. This command accepts options to specify the ID of an object and a .css file to use.
Write the content back to the .ui file instead of stdout.
The ID of the object to preview. If not specified, gtk-builder-tool will choose a suitable object on its own.
Load style information from the given .css file.