Recommended and mentioned products
Zim is a graphical text editor used to maintain a collection of wiki pages. Each page can contain links to other pages, simple formatting and images.
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
Have you tried Joplin? It is not something like Zim but you should check out that one.