Hi,
I’d like to reduce the icon size on the notification area so I can have two lines of icons in a shorter (as in less tall) panel.
Currently the icons shown are 22 x 22 pixels, but changing system-settings>Icons>Icons>Advanced tab>Panel size from 22 to 16 makes no difference, notification icons (clipboard, kmix, etc.) are still shown as 22 x 22, even after rebooting.
Any way I can change this?
TIA,
The icon and text size in the task manager panel scales automatically when the height of the container (default) panel is adjusted.
To get two rows of icons: right click on the task manager panel and choode “Task Manager Settings”, thin in the General section adjust “Maximum rows”.
Is that what you meant?
It is possible to configure the maximum icon size for the system tray like this:
https://forum.kde.org/viewtopic.php?f=289&t=131736&start=30#p365350
Thanks, eng-int, I’m aware of this - I already use two rows, as I like a panel larger than default.
What I’m looking for is two rows in the notification area to the right of the task manager, near the clock.
Like the task manager, the fast launcher widget also honor the number of rows in it’s configuration (I use it at the left of the panel, near the menu button). Only the notifications appear to set the number of rows automatically.
PS: See also https://forums.opensuse.org/showthread.php/522511-how-to-have-bigger-icon-in-the-system-tray?p=2809709#post2809709 for how to change the maximum systemtray (what you call “notification area”) icon size… 
Ah, perfect, thanks for the link. Although it just reduced the spacing between icons - maybe because the icon set I’m using doesn’t have 16 x 16 size, I didn’t check yet.
P.S.: notification area is a literal translation from pt_BR of what appears in the systray tooltip, thus the difference. Probably you see that in some german translations too - certainly in french and spanish. Sometimes I say something like “translated from pt_BR, so actual text may be different”, but didn’t think it would matter this time.
What size did you set?
You probably need 0, I think.
And note that this is just the maximum size. The icons will be smaller if the panel is not high enough. That might of course also explain why you don’t see a difference in size (because they were smaller than the maximum before already)…
P.S.: notification area is a literal translation from pt_BR of what appears in the systray tooltip, thus the difference. Probably you see that in some german translations too - certainly in french and spanish. Sometimes I say something like “translated from pt_BR, so actual text may be different”, but didn’t think it would matter this time.
Yes, I suspected that.
I just explicitly mentioned it to avoid confusion when I talk about the “system tray”. (which is called “Systemabschnitt der Kontrollleiste” in german btw, translated back that’s something like “system section of the control bar”… 
)
On my laptop, with a HiDPI display, the system tray icons are unaffected by the System Settings > Display and Monitor > Scale setting. This means that the default icon size is very small and stack into two rows with a medium height Default containing panel.
I am going to use Wolfi’s tips to increase the icon size a little.
Size 0, as suggested in the thread you posted. It only reduced the spacing between icons, so they actually touch it other, just short of overlaping. I also checked the icon sizes in a screen capture, they are 22x22 pixels. I don’t think this is the minimum because when I shorten (decrease height) of the panel, the icons in the “fast launcher” widget (translated from pt_BR ;)) also on the panel get very small, but not those on the systemtray. Unless the fast launcher kind of scale the bitmaps, and systray doesn’t, if this make any sense.
Now, the icon set is Oxygen, I don’t remember if it is standard or I installed it from system-settings. However /usr/share/plasma/desktoptheme/oxygen/icons only have app-specific svgz icons, and none for the systray that I could see.
Oxygen is not the default, Try the Breeze theme.
Or, make sure you have the oxygen5 packages installed,
Both Breeze and Oxygen5 (already installed) show the same behavior. I even installed oxygen5-icon-theme-scalable (a hefty 250 MB download), but no change after session restart.
However, some systray icons are not for plasma applications (syncthing, solaar, qsynergy), then perhaps they are limiting how much I can decrease the height. I don’t know.