Notes/To-Do list inside OH

I want ask, if there is any place in OH where I can write my remarks, or create a to-do list or place some manuals from the device to have all together ?

What do you mean ? Can you elaborate a bit more.

have a look on dokuwiki and some caldav servers like radicale…

radicale can be integrated into openhab.

To-Do list is quite clear, I want write my ideas what I want implemented into my automatization.
Because I have a special devices with special communication protocols, I want store documentation somewhere, because in the future it can help to trace a problems.

The short answer is no. OH is not built around the necessary concepts to host files like device documentation or track textual information. Most users will use some other system for this (I personally have my own mediawiki instance and task on nextcloud for these sorts of things).

The long answer is, with some creativity and effort you can find workarounds for these things. For example, you could store all the documentation files in the conf/html folder and then access them with /static/name_of_doc links. You could create a dummy script which never actually runs but you just use as a notepad for writing down your to do list and other notes.

I do have one set of information that I keep within openhab. For all the complex configurations I use for things like the bayesian statistic based items if have I developed a documentation page with swagger-like formatting that parallels the rest api docs OH uses, so that I can quick reference what I need when creating a new configuration or troubleshooting.

There is nothing build into openHAB. I would store my notes in github e.g.

In addition to what’s been mentioned here, don’t forget that just about every entity in OH in the UI has a “Description” field that can take any number of characters. It’s a great place to document what it does, reminders, and important info you don’t want to forget.

There isn’t a description for Things but there is for each of the Thing’s Channels and you can override them for autodiscovered Things too.

Similarly, for Items, there isn’t a description field but you could use metadata in a pinch.

Tags are also a powerful capability for identifying the purpose of something or to group collections of Things, Items, Rules and Widgets together.