What is the way editing a running app on windows?

There is no guranteed way to achieve this without changing the actual source code of the program.

There at least two obstaces to your idea:
1. While Microsoft specifies how resources such as strings are supposed to be handled, there are lower level methods to achieve the same, and programs could use any of those other methods. The program could even store and redraw everything as an image, rather than storing it as a string!
2. The memory that a program uses has very restricted access from other programs. That is a matter of security: if any program could simply modify the memory of another program, it could do all kinds of malicious stuff!
3. While memory addresses used to correspond to phyical addresses 30 years ago, nowadays only the memory manager knows the true physical address. Therefore, even if you find a physical address that you can modify to change a currently running program in any way, it will not work the next time you start that program, because then all addresses will be different! These kind of techniques may work on some embedded systems which do not use virtual memory addresses, but not on modern operating systems.

It doesn't matter that it's "only for current session and only for one time". It is extremely difficult to do this. There are a number of different ways applications can store strings in memory. What may work for one string in one app may not work for another string in another app.

The technique you find works for one application may not work for another.

FindWindow and SetWindowText will not change the data string in an arbitrary address in memory. It will only change the DISPLAYED string in a control and that's not even guaranteed.