Any (and all) new Trainz installations will install themselves in their own folders separate from any other existing installs. So you could, for example, have Trainz (original version), T:ANE, TRS19PE, TRS22 and Trainz Plus (from your timeline) all installed and all running independently of each other - although why you would is a different question.
The Trainz core directories (i.e. the software) will be installed in one location. In my case:-
C:\Program Files\N3V Games\Trainz Railroad Simulator 2019 (this is my Trainz Plus install as I originally upgraded to Trainz Plus from TRS19PE)
C:\Program Files\N3V Games\Trainz Railroad Simulator 2022 (this is my Trainz Plus beta version install which I have used for past Trainz+ beta version testing and will use again when the next beta is released)
I only have Trainz Plus installed - all earlier versions have been binned.
Currently the two installs are identical with the same build numbers (119450) but the second is set to the beta stream.
The Trainz user directories (where all your downloaded and installed assets are kept) are also installed in different locations. In my case:-
C:\Users\[Username]\AppData\Local\N3V Games\trs22\build sd6ccvr61
C:\Users\[Username]\AppData\Local\N3V Games\trs22\build i0ok12iy1
... which can be confusing. The "build ......" is a randomly generated sequence of text characters. This is where your routes will be stored.
If you are not sure which one is which then check using the instructions below for finding the current user data folder location for each of your installed versions. Note the build folder name in each case.
First Step - if you have not already done so, then
On the Trainz Plus Trainz Launcher screen click the button Trainz Settings and then the MyTrainz tab. Enter your username and password (both are the same you use for this forum) and when you get the accepted notice, exit Trainz back to the desktop (close the Launcher).
Second Step - locate the user data folder(s)
Then start the Trainz Plus Trainz Launcher again and select Trainz Settings again. This time click the Install tab. You will be shown the user data folder location for your Trainz Plus install. There is also a link to a web page that gives instructions for moving your user data folder to a different location, such as on a different drive.
You can select a different folder, such as your current TRS19PE user data folder, by clicking on the three dots next the the current folder name and then navigating to the folder address (the folder named build .........) you want to use.
In either case you will need to exit back to the desktop before starting Trainz again. The change will trigger a database rebuild.
Hope this helps.