Hi,
Since decompilation, modification and recompilation of apk required several commands so I created a java GUI tool APKRepatcher which helps you to modify an existing apk using a simple user friendly GUI. It lets you edit java/smali code from an APK and rewrite the changes back to the modified signed APK. Additionally, it provides you option to convert Dex, Jar, Class, Smali, Class from one format to another.
[Link removed]
Thanks