how to draw free drawing
Screenshots from LibreOffice 220.127.116.11 on Windows 6.3.
I don’t want to draw a mind chart in the sense of a free pen
LibreOffice has a drawing component called Draw. With it you can mainly insert shapes and as @LeroyG already mentioned there is a freehand pen.
But LibreOffice has no component with which you can paint. You can find some free programs on the internet. As an example, Gimp is mentioned here.
Maybe you want a Flowchart (mind map?), in which case you do need to use Draw as Writer doesn’t seem to have connectors for the objects. You can always embed a Draw object in Writer later.
Note: the Draw is a vectorgraphic editor, but not a pixelgraphic editor.
I know that you mean the ready-made models and then I deliver them. I do not want that. I want a program belonging to Libro that serves this purpose
Impress is the presentation program, similar to PowerPoint.
It seems that the FreeForm Line tool that @LeroyG suggested is the tool that you need. It is available in Impress and Draw. Double-click it to keep it selected. It uses the Object without fill drawing style which you can modify beforehand as I did, or you can change the style or the lines after they have been drawn.
Not so good to write, because it simplify and round (?) some sharp edges. I can’t find a way to change this behavior.
True. I have poor handwriting so always use the keyboard. In that case I would probably use Freeform Line Filled, double-click the object and type text, possibly having chosen a handwriting font like Comic Neue
Then you have chosen a wrong tool. Create this image in a third party pixelgraphic editor, ant then import the image into your Impress document.
The tool is useless
As you are right
I don’t have any other free program
And this is the problem
There are many free (and/or) open source pixelgraphic editors.
Just search them with Google.
“GNU Image Manipulation Program (GIMP)” for “GNU/Linux, macOS, Windows and more”.
The calligraphic pen in Inkscape works the same way as normal editor but the result can be saved as SVG if required.
Krita might be worth considering too