I've used and tested several apps in the last 5 years or so to manifest my thoughts and ideas in an efficient and intuitive way. Here you can find some of the apps I currently use for note taking and visualization.
- Notion
An allmost alround note taking web app with a WYSIWYG editror. It has a great free tier with almost no limitations. You can create spaces and nest notes. There are plenty possibilities to structure your notes in tables, embed links and rich text formatting. You can also share notes to others via public links. It also has a desktop and mobile app, which is very useful. This is my current top note taking app I am using for almost everything. - Milanote²
This is a simple mindmap-like web app where I mostly throw together ideas, articles and tech stacks for projects. It is very easy and intuitive to use. The only downsight is that the free plan is sort of restricted in usable working space. - Google Keep
Very simple notes taking app which also has a great mobile app. I mostly use this app to set reminders and If I need to take notes very quickly which I also need on other devices. It also provides a desktop and web app. - Samsung Notes
A default app on Samsung Galaxy Note devices which works very well with the S Pen. I use this app very much for note taking with my mobile phone, but it lacks main features like searchability and syncronization with desktop or web apps. But I use it very often, so I wanted to mention it here too. - Miro
A very extensive white board web app with a lot of integrated tools, features and templates. It has great features for presentation and collaboration and I used it a lot during my work as a software developer to design and visualize projects and software designs. Sadly, the free tier is very restricted and payed plans are a bit pricy. - Obsidian
A great application to create knowledge databases which are stored in a local file system using markdown files. This is very useful to create knowledge vaults like this one here but you need to take care about syncing your database yourself. But there are great user plugins like obsidian-git which makes syncing your database with a Git repo very easy. It is completely free and has a very intuitive UI. It also supports backlinking. - diagrams.net
Formerly draw.io - a nice web platform to build charts, diagrams and visualizations. It's free and even open source. - excalidraw
Another very awesome drawn visualizations web app.
² This is a ref link where I get more features when you sign up using this link. I do not receive any money through this referal link though.