With you having Trainz registered since 2016, I imagine that the above posts, explaining how to create CDP files and save/transfer them, was not really what you are looking for ..? yeah, no, don't answer that.
SO, hypothetically, it depends on WHAT assets you are talking about, and where/how you got them ... (I have 4 computers with different versions of Trainz, so I am speaking to transferring Assets between each of the 4 systems ..where those systems are located matters NOT)
1. Third Party freeware downloads can be saved to CDP, or just copy the CDP you already downloaded, and installed on a second, or third, or tenth computer.
2. Third Party Payware .. Same rules apply, though some may be password protected .ZIP files (rare) and you'll need the password for those.
3. DLS, downloaded from DLS from within your Trainz Content Manager ... can be saved to a CDP, and transferred to a computer without internet access, as mentioned in above posts.
4. DLC, downloaded "payware" bought from N3V ... CAN NOT be easily saved to CDP and transferred between computers, due to the way the Texture files are compressed, AND due to their being linked to YOUR account at purchase/initial install
If you have another scenerio that is not mentioned above, just ask, hypothetically.