Is there a simple way to do that without having examine the plots?
May be there is a build in way to this using using DynamicSystems (i.e. give it transfer function and omega (rad/sec), and it gives back the gain in db unit at that frequency).
I do not know now. I do not use DS very much these days.
But you could always just apply the definition of the gain itself. Given TF = f(s), just replace s by I*w and find the absolute value at the specific w you want, then do 20*log10 of he result. This gives the gain in db at that specific w. Here is an example
Let us verify by evaluating the gain in db at say w=0.1 and w=0.2 and w=0.6 and w=1 to see if we get same result as show in the above
Which matches the plot.
You can make small function and put the above code in it. somethging like
restart; #we do not need DS
And now do