If you keep source code in Dropbox you know the pain, it tries to sync every node_modules and dist folder and just sits there churning. Dropbox Sync Skipper is a small free app that lets you mark folders to skip in bulk instead of doing it one by one.
You pick a folder, type in what you want to skip, node_modules and dist for example, hit search and then ignore. It does it the way Dropbox expects, alternate data streams on Windows and extended attributes on Mac and Linux, so your files themselves are not touched. There is an unignore button too if you change your mind.
It is version 1.0.0 and it is a Wails app, so it is a proper little desktop program for Windows and Mac with downloads straight from GitHub. Linux is in the source if you want to build it yourself, though the developer says Dropbox testing there has been minimal. The page does warn you to use it at your own risk, which is fair for something poking at file attributes, but for a dev folder full of build output it beats syncing gigabytes of stuff you will never open on another machine.
Product page: https://jun-murakami.web.app/apps/dropbox-skipper