I thought it would be useful to have margins, paddings as well as ability to set them as different, for several different cases, so I made extension that provides us with that functionality. Here it is its complete code, aix file, so that you can immediately use it, as well as a simple demo application that showcases its use: https://github.com/Tomislav-Tomsic/GUI-Extension
Code license is Apache one, which means, as much as I can bother with it to understand, you can use its code for whatever you like, except that one has to be polite about it, say where it is from etc. (At least, that is how I understand it).
Problem is, it might have too much functionality, it might have been wiser to separate it in several different extensions. For instance, one can put all visible components (that is, a subclasses of AndroidViewComponent) into a list, which one can than manipulate as one wants or can. One can also have choices in putting visible components of same type and thus "unlock" additional feature. For example, ensuring that all members of such lists, buttons or label for example, have same width, height, font color etc. Like I said, it might have been wiser to separate it into several extensions.
Animation extension on the other hand, is comparative breeze. It is simple and straightforward. One can now animate one's view, move them (translate I mean), scale them, rotate, as well as combine those as well. Hence, we now can play with the user interface more broadly. Naturally, I didn't test it for all imaginable use cases, I hope others will jump in with their own ideas, but for what I did, it works.
Only problem that I see with it, which actually is the one that GUI also shares, is in the method and argument names. I am not an English native speaker, and I simply couldn't think of more meaningful, shorter ones. I hope others will have better ideas.
In any case, here it is: https://github.com/Tomislav-Tomsic/AnimationExtension
Again, its full code is available, under the same Apache 2 license, and again you will find its aix file, and the same simple demo app, built with MIT App Inventor 2, and then tried on my Android devices.
I hope you will find them both useful and enjoyable.