Bug 300862 Change buttons order in PathVariableDialog
IMHO more intuitive order for buttons in PathVariableDialog would be [File...][Folder...][Variable...] instead of [File...][Variable...][Folder...]. I can provide a patch if the swap makes sense to you too ;)
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/PathVariableDialog.java
IPathVariableManager pathVariableManager2 = currentResource.getProject().getPathVariableManager();
			String[] variables = pathVariableManager2.getPathVariableNames();
    		String internalFormat = pathVariableManager2.convertFromUserEditableFormat(variableValue, currentResource);
    		URI uri = URIUtil.toURI(Path.fromPortableString(internalFormat));
        	URI resolvedURI = pathVariableManager2.resolveURI(uri, currentResource);
        	String resolveValue = URIUtil.toPath(resolvedURI).toPortableString();
        	
        	 
        	String[] newVariables = pathVariableManager2.getPathVariableNames();
        	for (int i = 0; i < newVariables.length; i++) {
        		boolean found = false;
            	for (int j = 0; j < variables.length; j++) {
            		if (variables[j].equals(newVariables[i])) {
            			found = true;
            			break;
            		}
            	}
            	if (!found) {
					try {
						pathVariableManager2.setValue(newVariables[i], null);
					} catch (CoreException e) {
						
					}
            	}
        	}
        	return resolveValue;
        }
        return variableValue;
    }