Desired Capabilities - The Missing Manual

Ok Im going to go back and retrace my steps

Is there anyway to change the preferences inside the Dictionary type at run time?

I’m using Chrome 77 and I have the prefs Dictionary in my Desired Capabilities -> Web UI -> Chrome settings. The two properties I have in the dictionary are download.prompt_for_download = false and safebrowsing.enabled = true. Before adding these, Chrome would give me the keep/discard prompt immediately upon clicking the download button. After applying them, the file appears to begin downloading, however, when it gets to 100% it shows the keep/discard prompt instead of finishing.
Am I missing a property in my prefs dictionary?