How can I add a folder that's on another drive to Dropbox?

My C drive is a NVME m.2 high speed drive and D drive is a pretty slow old drive. I have my Dropbox folder on D:\Dropbox. Normally I do my programming stuff on C:\projects, since C drive is fast and I need to complete the code compilation as fast as possible. Is it possible to have Dropbox protect my C:\projects without copying it under D:\Dropbox (D drive doesn't have enough space, but my Dropbox account has plenty of space)? By protect, I mean sync the stuff to Dropbox server. It it possible to put a pointer under D:\Dropbox\projects_pointer and basically tells Dropbox, please go to C:\projects to find the files under this folder?

Looking over the official Dropbox documentation on symbolic links, etc. (the way this type of thing would normally be accomplished), linking (pointing) items to your Dropbox folder likely wouldn't allow them to be protected. And this excerpt from how to move your Drobox folder explicitly states:

Dropbox doesn’t support certain types of files and metadata like symlinks, aliases, shortcuts, junction points, resource forks, and networked folders.

As background, this blog post claims that support for links to external files and folders was apparently unsupported (but worked) in the past, then disappeared in mid-2019.

Solutions(?)

You could (of course) move the Dropbox folder to C:\ and create your projects folder under the Dropbox folder itself, but that might not be ideal.

There is also the possibility of using a script or command-line client to bypass the Dropbox folder for uploads. This wouldn't be "pointers", but it would allow the folder in question to be backed up to Dropbox.

As examples, Dropbox is written in Python and has an official Python API Client module or there is the (arguably simpler to use) self-contained dbxcli command-line client. Either of these could upload your C:\projects folder periodically via task scheduling or by manual invocation.

One caveat here would probably be any automatic syncing back to your Dropbox folder (since you specifically mention a lack of free space on D:\). If you wanted to implement either suggestion above, you would also probably wish to investigate selective syncing of folders in the desktop application.