Yesterday suddenly the pictogram from dolphin appeared left from the start button.
Now every time when I think that I open the kde menu, dolphin starts up because I click the wrong pictogram.
How can I remove it?

frameworks yesterday 5.18, today 5.19
kde-plasma 5.5.4

try this:

open up panel settings (left click icon on the panel's far right) then right click on the dolphin "pictogram" and select remove

Then a new panel appears

[screenborder] [heigth] [add widgets] [add panel separator] [more settings]

(translation may not be perfect)
Is that what you meant about the panel settings?
i can't see any pictograms in there.

yes, you would then hoover over the "pictogram" in the panel and remove it, the new "panel" not only displays additional panel options but also enables the removal of icons or widgets in the panel.

YEAH!
Thank you very much for your help!!

Is was a little confusing that I had to open the settings panel and then go back to the original to remove the pictogram.
Ok no more dolphin by accident :-)