I've been a steam user for a couple of decades, and the windows app has an issue that has always really annoyed me.

When adding a new download the queue, Steam automatically gives it priority and starts the download, pausing the one in progress. This is really annoying as I keep having to switch to the library to manually resume the original download.

Steam NEED to change this so the current download isn't interrupted, or make the queuing mode switchable in the settings.