Control Panel->Keyboard, viz:
@
MarjaE - it's a global setting, it seems to apply to all programs. I just tried it in
calibre, Sigil and MalwareBytes (they use various versions of Qt). Also tried File Manager, MS and Libre Office, a couple of text editors, three browsers, some Fluent apps (Settings, Snip and Sketch), and an old Win98 program I run in compatibility mode - they all had a non-blinking cursor when I set the slider to None.
BR