Thanks for your report.
I have sent you an email with a debug version of WinSCP to the address you have used to register on this forum.
When I try to add external editor (PhpStorm) it happens.
<If relevant, consider attaching a session log file or a screenshot)>
WinSCP 5.9.3
Error message:
Invalid access to memory.
Stack trace:
(001F01A4) Vcl::Graphics::TFont::GetName
(0008147F) ntdll.dll
(0006F02A) ntdll.dll.KiUserExceptionDispatcher
(000913FE) SameFont
(007B4869) TRichEdit20::SetFormat
(007B67C4) TEditorForm::ApplyConfiguration
(00061E7A) TEditorManager::ProcessFiles
I know how to reproduce the problem or the problem happens frequently enough. I wish to be contacted by the WinSCP team to help resolving the problem.