Whether or not Vernier Video Analysis prompts for a file name and location when saving a file depends on your particular browser settings.

Vernier Video Analysis has a Save As.. option in the file menu. What happens at this point is dependent on your browser settings. If you have set your browser to automatically download files to a certain location (often a Downloads folder), then you will not have the option to give the file a descriptive name; a file named using the pattern Untitled_1234.vmbl will be saved.

If you prefer to give Vernier Video Analysis files a descriptive name or specify a location, you must set your browser download preferences to “ask every time” (or the equivalent). Go to your browser preferences, and search for download settings.

If the browser is configured to ask for file locations, you will be prompted each time for a file name and location.

The option is called “Always ask you where to save files” on Firefox.
The option is called “Ask where to save each file before downloading” on Chrome. Find this setting at chrome://settings/downloads , even on a Chromebook.
The option is called “File download location” on Safari.

Also see How do I save and open files from Vernier Video Analysis on iPadOS or iOS? for iOS-specific instructions.