Walling is described as 'Working on a project, researching a topic or writing an article? Walling makes it easy to break down your ideas, refine them and visually organize them' and is an app in the Office & Productivity category. There are more than 100 alternatives to Walling for a variety of platforms, including Online / Web-based, Windows, Mac, SaaS and iPhone. The best alternative is Joplin, which is both free and Open Source. Other great apps like Walling are Obsidian (Free Personal), Notion (Freemium), Microsoft OneNote (Freemium) and Trello (Freemium).
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, can be copied, tagged and modified either from the applications directly or from your own text editor.
With so many tools, it's hard to keep everyone on the same page. Notion is a new tool that unifies them all. It's like Google Docs, but everything is organized and discoverable by your team. Real collaboration in real-time.