Hi there Taly!
So for formatting strings we can use the actor "Text Formatter". Double click on the actor and a little window will open, in that window we can use the P (for parameter) followed by an index starting from 1 to say what parameter we wish to use.
So let's say we have the text
and we wish to change the text after the = to do so we use the following.
If we now press OK, mutate the input of the param 1 to text (simply connect an trigger text to it) we now see that when we change the Trigger Text input / trigger it that the output of the Text Formatter changes.