I have fixed the indentation problem:
Issue 2374 – Directory tree indentation is scaled incorrectly when starting on scaled display on system with scaled primary monitor
As a side effect, it also fixed the clicking problem.

The arrow color issue is tracked here:
Issue 2133 – Light tree arrows in dark mode
It's Windows problem, imo. And as stated above, it's not new in 6.5.

Please post equivalent 6.3.7 screenshot.

I have the display issue since upgrade to 6.5.x. Before, everything was fine. currently I working with version 6.3.7 and see no issues.

Thanks. I was able to reproduce the problem now. I'll look into it.

Though I can see the color problem on 6.3.7 too. It's not new in 6.5, right?
Also 6.3.7 seems not to scale the lines at all, so it wasn't really behaving correctly, it just had the opposite problem than the 6.5 has.

The notebook has a 2560x1600 display, and an external 4K monitor is connected, both set to 200% scaling. WinSCP launches on the external primary monitor.

Thanks for your report. Please post your display/monitor setup. Their number, resolution, scaling. Which display is primary one. On which display do you start WinSCP. Thanks.

Since updating to version 6.5.1, my folder panel looks like attached.

Observed issues:

1. Unusually long lines in the folder view
   
2. The arrow (e.g., for the "Intel" folder) is missing when the folder is expanded
   
3. The arrow is also not clickable
   

System: Windows 11 Version 24H2 (Build 26100.3775)

EDIT: I downgraded to version 6.3.7 and all is fine again.

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Additional issue with the forum:
The "Preview" button works the first time, but after previewing, I get the following error when trying to post:

General error – Sorry, your post was not accepted. Please, make sure you have JavaScript enabled.

JavaScript is enabled, and the initial preview loads correctly—but after that, preview fails.