I’m using the free edition in my Desktop PC,
I want to see the data in Manager when I travel.
I installed Manager in laptop as well and use Dropbox to sync the files.
Can I make the laptop-end read-only so I can make sure nothing happens to original data?
No. The desktop edition, no matter where the data file is stored, is single-user. So no permissions are possible.
I really don’t think it should be that hard to put a file lock on the data file if it is open so that only one user can access it at any one time.
That was not the point, @scpantry. The point is that the free desktop edition is single user. If you want permissions, users, and access control, you must buy one of the paid editions. It’s not a matter of how easy or difficult something is. That’s just the developer’s business model.