I use a widget for the digital clock, most recent device, clipboard contents, networks, and volume.

Is it posible to have this widget always on top?

You can add a separate panel for them and use the panel settings to make them always on top.

airdrik wrote:You can add a separate panel for them and use the panel settings to make them always on top.

Thank you

Ps is it possible to put these widgets into Cairo Doc.

Can the Application Launcher be put into this doc. I have tried, but they willl not slot in.

I don't think you can add them to Cairo Dock as that is built on Gtk, while the Plasma widgets are built on Qt/Qml.
However, you might look into Latte Dock instead, which based on my rather superficial evaluation is very similar to Cairo Dock but built for Plasma.