UX feedback

@485397 @485429 I would like to ask for your feedback on the usability of the IMAGES CI pipeline.

Currently the pipeline for qemu or vbox is created when the respective keyword is found in commit message. But I remember both of you asking how to run the pipeline manually, which tells me that it is not intuitive.

So, would you find it more intuitive / easy to use, if the whole pipeline was created every time, but the build jobs had to be manually started via GitLab UI? Or do you maybe have other ideas how to improve it?