Thanks for your report.

It's probably yet another instance of this issue:
https://winscp.net/tracker/1463

I've further improved the fix.
I'm sending you an email with a development version of WinSCP to the address you have used to register on this forum.

Brand new installation of WinSCP 5.17.3, machine is Windows 10 Home (64-bit).

Installed using the default settings (tried a couple of different custom installations, no difference).

Login / Site Manager dialog box does not have the "Tools" and "Manage" buttons (see screenshot).

(Screenshot is populated with various saved sessions, obtained by manually copying in a pre-built WinSCP.ini file, however issue was present on first startup, before doing any configuration at all.)

User has vision problems, and so runs with enlarged fonts and reduced monitor resolution; this may be relevant. Seems as if it may be related to old issue https://winscp.net/forum/viewtopic.php?t=5205.

Tried resizing login window, however issue persisted across resize.

(Sorry, no logfile is available; this was being done remotely, and the user was unable to find the logfile -- logfile issue is related to user, not to WinSCP.)