It would be great to have tables with filter options (DataTables).
Example: https://datatables.net/ Fore example this DokuWiki extension added it: plugin:datatables [DokuWiki]
I recently added a “health”-log, with the following columns: symptoms, diagnosis, treatment, remarks.
Therefore it would be great to have a filter, e.g. when I want to know at what dates I had influenza in the past.
My two cents: I log a lot of things too and rely a lot on efficient searching.
I do not put lots of entries in a large table.
Instead, each entry is a note. Each note title is carefully designed (prefix, keywords). Note body is either empty or sometimes has useful extra info.
Then I use search to quickly get the info I want (e.g. at what dates I had influenza in the past => year+month is usually a prefix of note title thus search result already give me that info).
The key thing here is to use the Embed Search plugin. You can hardcode searches with notes, which once well set up is very powerful. Link: GitHub - ambrt/joplin-plugin-embed-search: Embed search inside note. Joplin plugin
I'm using inline tags to filter my logs with this plugin (screenshots below). You can use it to show very specific lines from a single note, or multiple notes. In addition, if you use multiple notes (such as one for each day, or each month) and tag them with inline tags, or use front matter, you may also summarise the result in a table (one row per note).
Thanks a lot for the ideas and recommendations. I will give it a try 
You could use the Markdown table: sortable plugin and sort by column “diagnosis”.
