Can I exclude papers from my CV/Google Scholar when my contribution was marginal?
Can you? Yes. You are free to curate your Google Scholar page as you wish, and you can easily re-title the &quot;Publications&quot; section in your CV as &quot;Selected Publications&quot;.
Should you? This is probably the more difficult question. I don't think your case is that unusual: I can think of a few people who have publications from 'a previous life' as a scientific software developer or lab technician before they started their PhD. I don't think anyone is misled by their publication lists - there's usually a fairly obvious transition into a more focussed area around the time they started their PhD. This is all the more true in the case of a CV, where (presumably) your pre-PhD employment is already itemized. I think people are far more likely to wonder why you have omitted certain papers than wonder why you kept them in.
I would argue that you should keep everything on Google Scholar. It is fundamentally an interface to a search engine, and users landing on your page may come with a variety of motivations. People can always 'sort by year' if they want to find your recent work. The only people who would seem to be seriously inconvenienced by you keeping everything are those who want to judge you solely based on your citation statistics - and do you really want to make their lives easy?
For a CV, the obvious choice is to explicitly divide your publication list into two sections: pre- and post- PhD commencement (or perhaps &quot;Publications in &lt; main research area &gt;&quot; and &quot;Other publications&quot;, if that's a neater division). This would seem to strike a good balance between completeness and offering an acknowledgement that not all your publications are equally relevant to your current career. In circumstances where you need a 'short-form' CV, you might then compress the &quot;Other&quot; section to a brief summary sentence, perhaps with a link to a full listing on your website.