Never mind then… it is probably not as straightforward as the table solution. What I focused on was the data processing in the background, creating the basic for other data to process at the point of note taking. What’s a single element? How do we reach and where do we store that single element? If it is necessary to add another data dimension or add another data relation.
But I will try to portray the possiblity again.
Hierarchy defining for relations at library - Workout>Push-up>Set>No. Workout>pull-up>set>no. We can trace the hierarchy, regardless the location of fixed hierarchy. Push-up is always part of workout. It doesn’t require multi-dimension.
If we have a place to create structure (as template or table or at library), it can be considered as one frame/dimension of a group of data (no of push-up set or pull-up set), then we can pull structure information and one set of data within it. We can reuse the structure and make another layer of data. So that we can make it display another set of data if the structure is the same - making it embedded/reusable template or nested table.
The limitation to consider table as the solution to multi-dimensional relation is that it already defined the structure of multi-dimension, rather than letting user define the structure/hierarchy at the point of interest.
Like FR multi-layer text annotation (finally found the FR I was referring to), the structure is the text, the layered/dimensional annotation, gender and declination, is the data stored based on the text structure. Language learning will have multiple texts or essay (structure).
Or as the process of making forms, there are structure part where people filling in the form would not need to edit, and the input section they fill in ← Like FR form objects. Structure differs at contexts.
I definitely agree that matrix structure is a way to understand multi-dimension and table is the easiest way to understand matrix 
. There will be times where I want to use matrix table to layout my contents as well.
But it is not possible to use tables in the above use case of mine (Recalling ancient memories of learning about matrix 
). It is more than a single matrix. I would be doing at least matrix multiplication and managing non-commutative properties. All calculated element will become secondary part of a new matrix to make reference. The basic unit for me contains a combination of some kind, aka basic unit is one element in a one matrix.
Even if it works, it is not effective anyway. I might be only using one element of the matrix/table leaving the rest out as empty until they are useful. Of course having such table still concretises and visualise the used, missing, unneeded information. But can you imagine creating or adding a new dimension or a new matrix or row/column for every person you meet, every emotion you and the person have, every theory you know, at every moment in time? That’s already a 5x5 if we count one unit per dimension. The length and width of a set will not be easily navigable. Let alone the logic representation/argument that link each combination together and the non-linearity and non-structure of art (compared with taxonomy of science).
That’s why relation as object is more like the thing I will be using. This enables the greatest flexibility but allowing the making of linkage to show structure, and thus the ability to have a combination object within the matrix table.