I have used the Google Universal Analytics for many years and will now use Google Analytics 4 instead. So in Google analytics Admin I created a new "on-page tag" and placed it in my site together with the old UA tracking code. But should I have removed the old UA tracking code before or should I keep both the old one and the new one there?
Also, should I have used the existing "on-page tag" instead of add the new one, the only difference between them is the ID. The existing on-page tag has the same ID as the old UA code, but the new on-page tag has a new ID.