Hello and welcome.
Variables are not capable of being documented because they are user defined and can/will change depending on who is writing the code and what kind of code is being written. However, you can get information about a particular variable by highlighting it and hitting the F7 key. This will show you all the places where the variable is used, including the most useful place for figuring out what it represents, the place where it is defined in code (ex. Dim qwertyuiop as List). Once you see what the variable's type is, another useful way to see what you can do with that reference is to type the reference variable followed by a "." (without quotes), like this: "qwertyuiop." This will trigger the auto complete helper to show you what is available. The next helpful thing is to trigger the auto complete again for a particular function by putting an open parentheses after the function name, like this: "qwertyuiop.Initialize(" which will then show you what parameters the function requires.
In addition, you can also type a single function name into the search box of the forum and the first line item in the results will be the online help entry for that function.
Oh, and the object browser is very helpful too. If I remember correctly it will even pull the functions out of external libraries so you can get a glance of what is available there as well.
Finally, I am currently in progress creating an online video training course that will help with the learning curve in a more sequential way than digging through the forum. Although, as mentioned in your own post, the beginner's guide, user's guide, the B4a book by Phillip Brown and the 'tutorials' part of the forum are all great resources to get going with. I know there is quote a lot of material in all those documents, but if you feel like you are spinning your wheels a bit, even working through the simpler examples will help you with getting the flow down.
Best of luck!
Eric H