> - why is drag handle area impossibly small? When I need to manually resize a window (or column) I need to have the mouse pointer on the specific pixel of the window border, or else I wouldn't get the resize pointer

You need to change the window decoration

https://docs.kde.org/trunk5/en/kwin/kcontrol/kwindecoration/...

"Tip

For accessibility purposes, some window decorations support extra wide borders. If this is available, you can also choose a Window border size here. The large borders are easier to see for low vision users, and easier to grab for people with limited mobility or difficulty using a mouse."

Holding ALT + right mouse button can be used to resize windows easily. (Left for moving them)

It's super/meta for me, not alt.

Yes, it's changed recently as Alt was interfering with too many applications (e.g.: Inkscape use it). Using the Super (Windows) key is less problematic. So it depends on your KDE version. Or you own settings: I have an "old" (Debian stable) KDE version with Alt by default, but changed it to use the Super key as the new default, for the same reason.

Wow! ALT +right works for me, Left doesn't (perhaps that is disabled on my system).

Great tip!

Works in XFCE too

> how can I see that a screen/dialog is active

I use "Dim inactive" desktop effect which darkens windows that aren't focused. You can configure the strength of dimming, so that difference active vs. inactive is clearly visible but you can still (somewhat) read the content of inactive window without activating it.