https://support.mozilla.org/en-US/kb/manage-downloads-preferences-using-downloads-menu
When I open a file with an application, why is it also saved to my Downloads folder?
Before Firefox version 98, files you opened in Firefox with an application were also saved to the system Temp folder on Windows and Linux, even though you may not have been aware of it. Firefox no longer saves files to a temporary folder because of the downsides to saving files in a location that is hard to discover. Instead, files are saved to the "Save files to" folder location shown in Firefox settings, in the General panel Downloads section under Files and Applications. (Firefox will not ask you to choose a folder when opening files if you have selected the "Always ask you where to save files" setting, to prevent unnecessary interruptions.)
Why do Firefox developers always assume that everyone is an imbecile? Why do they have to break useful functions because they believe their users to be retarded?