Is there a particular reason why mit app inventer doesn't offer the ability to change the package name of the app? Financial issue? Technical issue?
It's the most basic part of the app, and I found it uncomfortable that I had to find a way every time. After searching, it seems like a lot of people are uncomfortable with this part for quite a long time, but I wonder why it's not improving.
I thought there must be a reason why that feature is excluded from every update. 
Adding the feature to change the package name isn't the priority right now. The development team currently are working on iOS support, Kodular migration, and other bugs.
Since App Inventor is an educational platform, primarily that aims to teach Kids to code, adding a package name feature isnt the priority, but rather things like bringing iOS support etc.
Thank you for your response. I was wondering this because I think AppInventor is beyond the educational platform. Many users are using this platform for monetization. I think the strength of AppInventor is that it is easier than text coding and can create and release real apps.
Now, many people have already learned enough about block-coding logic when they are children through the "scratch" platform. They want to create an app that can actually launch, and it's a good motivation that it's easy to do so.
Use AI2Offline.
Taifun
I tried, but I got this error.
I can't access this link.
It looks like you have overseen the very beginning...
Taifun
Note: 
Please see this solution by @Anke. Thank you Anke.
Note: According to Mr. Pratim, the process ddescribed below is outdated. The package name now can be changed by:
Mr. Pratim described this process in detail here. Thank you!
See also this guide by Avram. Thank you!
I access this link Please see this solution by @Anke and I can't move on from step 3.
How do I run this black window and decompile the apk?
I installed apktool already but I don't understand what this means. What is d?
d = decompile
Did you install the "apktool"?
Yes. I installed.
Copy the APK in the installation folder folder and run (CMD)
"apktool.bat d yourApp.apk".
Thank you for your reply.
I'm in trouble again. I got packging errrors constantly.
I want to change the package name made in app inventor to my unique package name. In this case, how do I do step 4, 5? I'm confused about the folder and directory name from where to where. I don't have io/kodular~.
So what is that unique package name you like to use and what is the package name currently?
As you probably can see yourself, it would be wise to follow these steps only if you know what you are doing...
Taifun
I tried applying that tutorial to my situation. But it's hard to apply step5 to my situation. It's hard to apply the address of file path.
So following step 5a) by @Anke:
inside the smali folder you have to create the folder com and inside that folder com the folder dearsimple
Then copy folder memox into folder dearsimple
Taifun
Yes.
