Small beginner problems

1 - How to ungroup a drawing from a component?
2 - Can a closed form be filled with a color?

Claude Azoulai wrote

1 - How to ungroup a drawing from a component?

The tool for this is "Explode" and could be found in "Tools" menu under "Modify".

Claude Azoulai wrote

2 - Can a closed form be filled with a color?

Yes, the tool for this is "Hatch", found direct in the "Tools" menu. Check "Solid Fill" in the hatch option window and set the layer color to modify the fill color.

Tank you LordOfBikes
For the first question, great it works.
For the second question, I drew two rectangles one inside the other and the part between them is only partially filled.
See attached image

As I'm not sure, I attach the adrees of this image
http://www.claudeazoulai.com/Hachures.PNG

best regard

This behavior is a known bug with nested fillings, sadly not fixed yet.
See https://github.com/LibreCAD/LibreCAD/issues/826

A work around could be to draw two separate shapes (like L in your example) and fill them both.
The single shapes don't have any nesting and should fill properly.
This trick will not be visible in printings when the outline and fill color are the same.