Delphi 10 Seattle do NOT open last used project on start

Disable "Project desktop" in the IDE Autosave options (Tools\Options\Envinroment options).

But please do not open it when I start the IDE. Mostly I want to start or open another project than the last one

Granted, I do no have Seattle at hands, I settled in XE2. But try changing the shortcut.

-np: No welcome page. Does not display the welcome page after starting the IDE. np also stands for No Project. Independently of Environment Options Project desktop the last opened project will not be opened

http://docwiki.embarcadero.com/RADStudio/Tokyo/en/IDE_Command_Line_Switches_and_Options

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saving the layout and position of the tool windows like Refactorings,

That is what the "Layout" combo-box on the "Desktop" toolbar does. Unless you want different layouts in different projects. R-click over your IDE's tool buttons or go View|Toolbars menu to turn "Desktop" bar on. Alternatively use View|Desktops menu.