No, that's wrong. I've cleared 30GB, which has put space back on my C: drive so my swap and tmp files don't get crowded out. Space, and performance.
For the original poster: look in
C:\Users\<Username>\AppData\Local\N3V Games\TANE\build vqlfo3711
for a Backups directory.
I deleted these, (I don't need them) and cleared 30GB of space.
Nearby there is a cache folder, and I cleared the internet cache too.
As for the content - I used the content manager to find the dependencies of sessions I don't need, then deleted the ones marked "Installed from DLS". I can redownload them if the sessions and routes I want to keep show missing dependencies.
TANE seems happy, and my remaining sessions work fine. I'm guessing there's a DB somewhere that needs compacting, but I'm satisfied with what I've done so far. If the programmers are any good, they will have code that regularly cleans up the DB.
Now I just have to get a refund on the new PC I bought. What a useless suggestion.
I agree knowing what is a dependency or not is awkward. I've gone through the trouble of viewing content, and viewing dependencies recursively, but that's clumsy and really time consuming. It would be nice if there was a Dependency column we could sort on.
Your biggest culprit is your backups folder. Every time you edit or modify content, routes, etc., Trainz/T:ANE will make a backup of the content first should you mess something up you can then revert back to the original. This is why it take a moment to open the content for editing.
You can go into the backups folder and delete the older days, which are folders in YY-MM-DD format. FYI I cleared over 200 GB the other day!
Once you've reduced the number manually, remember to empty your recycle bin too, you can then set things up in the Launcher so the the program doesn't create more backups than you need.
At the Launcher:
Click on Trainz settings.
Click on Dev tab.
Set the number of backups to less than the default of 7 days.
I recommend keeping at least 1 day's worth in case you need to restore something from a previous session. Having this cushion here has saved me at least once or twice in the past and in that time I would have been totally SOL with my route edit.
Regarding disk space in general. T:ANE data can always be moved very easily to another drive should you decide to add in a larger disk. The program does run okay with data on an external drive, but I wouldn't do that for regular operation.
As always when manipulating data, I recommend performing a backup operation prior to ensure there's a safety net in place should something go awry.