I've been using evernote for a while now, but recently I've been thinking of switching to joplin. But ran into problems with the tag hierarchy.
I use a lot of tags in evernote, and established a set of self-tagging system, but when I exported all the articles from evernote, and imported into joplin, I found that the tags are only one layer, there is no support for hierarchical nesting of the plug-ins?
There is a plugin that introduces support for nested tags. That is, search for #parent to find also notes that are tagged as #parent/child1, #parent/child2, or #parent/child1/grandchild. Note that this plugin requires storing the tags in the notes' text ("inline tags"), which can be anywhere within the note (commonly, the first / last lines are used). If you find this useful, follow these steps:
Convert, using the plugin, your current tags to inline tags. By default, this will add them to the first line of the note (this can be changed in the settings).
Replace, using the plugin, existing shallow tags (#child) with nested ones (#parent/child), by right-clicking on a tag in the tag navigator panel and selecting Replace all.
Use the tag navigator panel to search for tagged notes, or even specific tagged paragraphs.
Will this plugin display a list of all the nested or unnested tags in a pane, like the default tag list?
Also, it seems the plugin treat any phrase starting with # as a tag. Sometimes we use # for different things, such as numbers (e.g., "Podcast #212") or color code ("#2E3440"). How should we rewrite the notes to differentiate them from inline tags?
It currently shows all the tags sorted (by name, or optionally by frequency), so nested tags appear next to one another. This view is different though from the standard Joplin / Evernote tag list / tree. It's the filter-while-you-type kind, and tries to save space on the panel. It has its pros and cons.
In the Advanced Settings of the plugin you may define an Exclude regex that ignores tags that match it. For the scenarios that you described, this could be #(\d+|[a-fA-F0-9]{6})$.
It's totally up to you whether to use one system or both. The plugin can sync the two systems of tags (from Joplin to inline, and from inline to Joplin, check the commands under the Tools -> Tag Navigator menu).
I'll consider it. The tag search panel is already a little too crowded in my opinion. However, I could add a third (!) panel with a list / tree of tags, that can be hidden when not needed. A click on a tag will update the search panel with results that match this tag.
EDIT: I could also try instead to add a tree view to the current tag navigation panel, so that a user may switch between a view of the notes in the open note and a view of all available tags.