How to deal with a piece of text and materials that you do not consider essential? How do you normally indicate a subsection, or a part of the text that it is not so important for the rest of text. Let me give an example:


  [...] This method uses ABC as a coefficient.
  
  Subsection: how to measure ABC
  
  [some text and a plot, making up for roughly one column]


The subsection can be skipped, but is probably too short to appear as an appendix at the end.
It depends a bit on your field of research.

In fields that have a somewhat strong relationship to mathematics, it is common that lemmas, theorems, examples, etc. are typeset in special environments. You can also typeset a note or a remark in such an environment, which allows the reader to easily skip over the part, and at the same time makes clear that reading this part of the paper is somewhat optional.

As an example, the publisher Springer provides a style file for the document typesetting system LaTeX for publications in their "Lecture Notes in Computer Science" series here. The documentation states in Section 8a that "note" and "remark" environments are available.

Here is how using a "note" in a paper looks like:



Note that there is no rule that prevents you from referencing to a figure in a note.