Is it possible to change the settings on the fly?

No. Settings cannot be changed on the fly. It is not safe.

If you need to slightly correct the settings, you should click on the original thread, all its initial parameters will be substituted in the appropriate fields, now you can change them and add a new thread.

Or you can stop the thread, call the context menu for the thread (RMB) and click on «Edit». The thread will be opened on the edit mode. After changing the fields, click the green «SAVE» button.