I used to be able to hide the KDE panel using.
qdbus org.kde.plasmashell /PlasmaShell evaluateScript "panel = panelById(panelIds[0]); if (panel.height > 0) {panel.height = panel.height * -1;}";
and unhide it using
qdbus org.kde.plasmashell /PlasmaShell evaluateScript "panel = panelById(panelIds[0]); if (panel.height < 0) {panel.height = panel.height * -1;}";
This would allow me to use a Virtualbox VM in, what I call, psuedo Full Screen… where the window has been stripped of it’s Window decorations, and it is set to Max Vertical and Max Horizontl.
In this psuedo Full Screen mode I can still access my other virtual Workspaces, but without the KDE Panel suddenly popping up as it would if I had it set to Hidden of Windows Can Cover modes.
Unfortunately this script seems no longer to work, since Plasma 5.27. Instead the panel reduces to about half it’s normal size… about 11 pixels (I have it set to 22 Pixels)
my system
Operating System: Manjaro Linux
KDE Plasma Version: 5.27.3
KDE Frameworks Version: 5.104.0
Qt Version: 5.15.8
Kernel Version: 5.15.105-1-MANJARO (64-bit)
Graphics Platform: X11
Processors: 4 × Intel® Pentium® CPU N3540 @ 2.16GHz
Memory: 7.6 GiB of RAM
Graphics Processor: Mesa Intel® HD Graphics
Manufacturer: Notebook
Product Name: W54_W94_W955TU,-T,-C
System Version: Not Applicable