Up until recently the changes done in the theme editor were not persisted automatically. It means that, unless the specific steps described here, were followed changes would be lost when the server is restarted. This is the case with all Nuxeo DM versions prior to 5.4.2.
Method 1: Registering the changes inside your application
Typically you will have to download the theme layout using the "More actions > Download theme to your computer" action in the editor's top menu. A file called theme-my-theme.xml (or theme-galaxy.xml if the nuxeo DM default theme is used) will be generated. You will have to register the file in your application using the theme service extension point:
This is the recommended method if the goal is maintainability.
Method 2: Customizing the theme
If the method described above is too complicated, you may customize the theme before doing the changes.
In the top theme editor's top menu click on the "Customize theme" action.
A file called theme-my-theme.xml will be saved on the server's file-system in the $NUXEO_HOME/nxserver/themes (Tomcat) or in $NUXEO_HOME/server/default/data/NXRuntime/themes (JBoss).
All the changes done in the theme editor will be stored in that file. To revert the changes, you may simply delete the file or click on the "Remove customizations" action in the editor's top menu.
Method 3: upgrade to Nuxeo DM 5.4.1
Starting from 5.4.1 the changes done in the theme editor are automatically saved on the file system in the themes/ data folder using the customization procedure described above which has been made transparent.
To revert changes and abandon all customizations, i.e. to revert to factory settings, click on "More actions > Restore original ... theme" action in the theme editor's top menu.