Is There a Mathematical Symbol For Mutable & Immutable values? As per above, is there a symbolical way of identifying a mutable value or an immutable value? As an example, in my notes, I want to denote the value 'Pi', 'Adam' as immutable, is there a symbol to represent an immutability of a value?

Even if there is one, your readers probably won't recognise your use of it and infer the meaning you intend, suggesting you need to introduce your own convention and make it explicit. Perhaps the simplest is to deitalicise your constants, viz. $\text{e}$ instead of $e$.