I used to play ts 2018 on my old laptop but it broke but if I was to get TS 2022 on a new laptop would all my DLC transfer over
Yes. Everything purchased on Steam will install automatically as it is tied to your Steam Account. 3rd Party stuff has to be manually installed again.
If I may make a suggestion, I would invest in a large external drive in order to make a back up of your Railworks folder, so if this happens again in the future, you will lose nothing. As said above, all your DLC from Steam will be downloaded again when you install train sim on you new system, but all third party DLC will not as Torfmeister says.. You will have to manually and individually download and install it all again. The potential issue is that if any of it has been withdrawn or became unavailable for some reason, then you have lost it forever most likely. If you had a backup of your Railworks folder, all you would have needed to do was install Steam, then drag a copy of the Railworks folder from your back up drive to your new computer... go make a coffee while it transfers, then you're up and running again with everything exactly as it was. It's well worth investing in some back up.
If the drive from your old system is still working you should be able to access and copy across your old Railwork directory (and any other files for that matter) but yes- in future make back-ups.
