I don’t think you will use this but I will note it.
When I look at text I think of it as a thought converted it into a linear form for conveyance of an idea with the text made up of glyphs. Those glyphs can be characters of an alphabet, emojis, symbols etc. or a mix of them. Understanding The Rebus Principle helps to explain how we arrived at present day writing.
Hyperlinks makes it possible to jump from a linear form to a graphical representation that is not limited to being linear or even being static, the representation can be interactive and/or multidimensional.
So instead of trying to expand and collapse data to/from a linear form, instead a link to a different representation might be better. This is one of the reasons I like using Cytoscape.js among many other means of representation.
When clicking on such links, as we know, it is better to keep the origin of the link on the screen at the same time as the destination and thus the need for more than one panel. One of my favorite demonstrations of this is the Reactome browser.