Yes, I can reproduce this in Win 10. Any maximized window (Schematic, PCB, Footprint editor + Gerber viewer tested) on the secondary monitor jumps back to the primary monitor if closed when it is maximized. It happens in both 6.01 and 6.99. This has not been a problem for me as I normally do not keep them maximized.
Perhaps slightly related to closed issue Regression in PCBNew/Footprint editor: Last used monitor not correctly detected on dual monitor setup (#4053) · Issues · KiCad / KiCad Source Code / kicad · GitLab although that was different?
My monitor setup is an FHD primary laptop screen, and a QHD secondary monitor with extended desktop. The position of the secondary monitor is adjusted not to align the top of the two screens, but so that mouse moves horizontally from one to the other low on the FHD screen.
(Interestingly, FreeCad 0.19 and possibly earlier versions has long had the the opposite issue: I have to keep it maximized, otherwise it moves partly over to the primary screen when re-opened.)
Application: KiCad (64-bit)
Version: (6.99.0-462-gb605d6d9ae), release build
Libraries:
wxWidgets 3.1.5
libcurl/7.78.0-DEV Schannel zlib/1.2.11
Platform: Windows 10 (build 19042), 64-bit edition, 64 bit, Little endian, wxMSW
Build Info:
Date: Jan 15 2022 21:08:15
wxWidgets: 3.1.5 (wchar_t,wx containers)
Boost: 1.76.0
OCC: 7.5.0
Curl: 7.78.0-DEV
ngspice: 35
Compiler: Visual C++ 1929 without C++ ABI
Build settings:
KICAD_USE_OCC=ON
KICAD_SPICE=ON
Application: KiCad Schematic Editor (64-bit)
Version: (6.0.1), release build
Libraries:
wxWidgets 3.1.5
libcurl/7.78.0-DEV Schannel zlib/1.2.11
Platform: Windows 10 (build 19042), 64-bit edition, 64 bit, Little endian, wxMSW
Build Info:
Date: Jan 15 2022 13:36:27
wxWidgets: 3.1.5 (wchar_t,wx containers)
Boost: 1.76.0
OCC: 7.5.0
Curl: 7.78.0-DEV
ngspice: 35
Compiler: Visual C++ 1929 without C++ ABI
Build settings:
KICAD_USE_OCC=ON
KICAD_SPICE=ON