Hi, I wanted to know if it is possible to make two different applications communicate with each other? For example, a control application, where this application can edit/change something in another application, and they are different projects.
Yes
For communication you usually use the activity starter
http://ai2.appinventor.mit.edu/reference/other/activitystarter.html
See chapter " Starting Other App Inventor Applications"
For this you might want to use an online database of your choice, for example CloudDB
Taifun
The easiest way would be to use an online database, change the values of specific tags when necessary, and on starting the other app, get the values of every tag, and perform the actions required.