I need a recommendation for a tree structured note-taking software

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.

myBase is a powerful yet easy-to-use knowledge management software that allows you to save and organize all your information in one place

A productivity and task management tool appropriate for both individuals and businesses. With Nimbus Note users can create notes and to-do lists, share them with others, and archive important data.