this is a basic guide to download the any file with the exact filename from download URL using On Download Start block from web viewer component.
just do the exact block arrangement which is shown below.
components used -
I hope this will help some users who wants to save file with the file name given in the download url.
i also updated the T-Browser (Open Source Version) with this download logic. if you want you can download the aia file from original post given below