thanks for your feedback, and sorry about my delayed answer. There was no notification despite your responses.
this request is related to plugin cb last views tab. last views tab shows different behaviour than friends tab, I suspect that our joomla template somehow interferes with community builder.
anyway, my question is still: when I use the backend to edit cb_fields, what can I do to alter layout values?
when I enter: "display:none" it simply shows this text as a message under the canvas Image.
What I want to accomplish that the canvas can be used in the profile to make the profile look better.
What I do not want is to display the canvas image in the last.views.tab, or to show it like it is intended in the preview that Astrid has shared.

What would be your advice?

You can't put css in layout fields. And you can't change layout in backend for last views tab. Either you inspect your page with a webdeveloper option in your browser to see what goes wrong, or you try to set Protostar as default template. When it shows OK in Protostar, then it's related to your template.

here is the screenprint when I use protostar as deafult template. to me this still looks different and I am not sure how to proceed with the analysis.
Maybe, when you have an idea what I should lookout for..

There must be something wrong in your installation/tab settings/field settings.

thank you - updating the last.views tab plugin was the solution!