Use the denote-wordcloud package

The denote-wordcloud package by Alexander Kuzmin presents a “word cloud” for keywords in Denote files. Each keyword includes a count for the number of times it is used. More frequently used keywords have a larger font size. The word cloud is interactive: clicking on a keyword opens a denote-dired buffer that matches all files with that keyword.

The documentation of the package also includes a demonstration: https://codeberg.org/treflip/denote-wordcloud.