Q: Will my paper be considered a case of self-plagiarism or salami slicing?

Detailed Question -

About two months ago, I submitted a paper on the development of processing methods in a specific field and it is now being reviewed by the journal. After writing the paper, I learned that it has certain limitations. (Of course, I have included the limitations in the discussion section as well). Therefore, we did some additional experiments to overcome the limitations of the technology proposed in the paper. We completed the development of the improved technology and started writing a new paper. However, during the preparation of the new article, I learned about self-plagiarism and salami slicing. Even though the core of the paper is "to develop improved technology over conventional technology," it is similar to the previously submitted articles. The main problem is that the material used is almost the same as the base data. That's why I am hesitant to prepare a new paper. The points which are currently troubling me are as follows:
1) Regarding the already submitted paper, the same topic is rare in that field, and the content provided in the paper is also very useful for readers. Therefore it is difficult to cancel/withdraw this paper.
2) The contents of the submitted paper and the content to be created in the new paper are too much to be condensed into one single paper. I think that the technology presented in each paper is totally different. (For example, current control mode and voltage control mode system)
Please advise.

1 Answer to this question

Before preparing a new manuscript about the improved technology, you have to carefully consider whether it needs another publication or if it can be added to the previous article as an addendum. If the new technology is just an extension of the previous technology, it might not warrant another publication. In this case, it might be considered salami slicing, that is, breaking up a single research paper into their “least publishable units,” with each paper reporting different findings from the same study. A set of papers are referred to as salami publications when more than one paper covers the same population, methods, and research question.

However, if you feel that the new technology merits a separate publication, you can consider publishing it as the second part or a follow-up to the previous paper. In that case, you should cite the previous paper and make it very clear that the current study builds on this one. To do that, you must wait for the previous paper to be published or at least accepted by the journal. Once it is accepted, you can cite it with the words "accepted for publication" in brackets after the journal name. Additionally, you should clarify in the cover letter that you have another paper on a related topic and provide a copy of the previous paper with your manuscript at the time of submission.