There isnt an OID for everything you might need to have. However, the answer lies within the interface. As Normis says, you already used a command to show the OIDs. In the same case, the radio certainly knows what the SNR is, as well as many other valuable metrics. The radio is calculating, or acquiring from internal hardware the SNR value, and RouterOS is displaying it. In using MT for years, I have learned that if it is displayed somewhere, it is a value that is available, but not necessarily through SNMP.
Enter into the world of the command line, and then graduate to scripting. Try manually 'getting' or 'setting' values in areas you are familiar with. Once you discover how to create your own variable for the value you desparately need (as always!), use the Dude ros_command, and grab the value of the variable you have created. It can be created with a script if necessary, or you can carefully execute ros_command statements right from the label in the device icon, as you would have using the oid. You will have then created your own set of 'oid's' that will become very useful in all areas of monitoring using The Dude. It takes a while, and is frustrating at times, but when you figure out that the radio has it, you wont be far from displaying or using the value in many different ways. Some command line techniques are quite esoteric, and you will swear all night that you 'just tried it before and it didnt work', and suddenly it works, but you just cant remember how you got there.
Discover the ways of the Mikrotik paradigm, i.e. knowledge and an open pallete of capability that ROS delivers allows the operator to create whatever environment works for your specific application. Thats the only way I ever figured out how to develop 'never before seen' displays. These things are a great benefit of the ROS environment, but at the price of finding the correct way to extract the functionality and/or data yourself.
You will feel great accomplishment once something finally works and is just what you needed.
BTW, learn by example (hint, hint). There is a great wealth of knowledge in the scripting section of the wiki. There are many examples of working scripts that show you how to do some not so obvious tasks. I know it helped me a great deal, and we really owe a lot to the many gratious developers who have submitted these scripts. There is no shame, and in fact, there is great joy in cutting and pasting something, and it works!