Open as in Windows 10.

Open a schematic "simu" in Windows10, Open as SimulIDE does not work.

Not sure how are you doing it.
But you should provide full path or add simulide bin folder to PATH.

When I tray to open a simu project from the file explorer, the following message appears; "THIS APPLICATION FAILED TO START BECAUSE IT COULD NOT FIND OR LOAD THE QT PLATFORM PLUGIN WINDOWS" in Simulide 04159. The path in W10 is previusly assigned to the simulide directory and its executable simulide.exe in bin the directory.

I will have a look.

As an alternative you can just drag and drop the file into simulide.