How to re-use textures assigned to materials or move them to the shelf?

[Sekuta]

I have not found a solution for this frustrating problem so far.
When I set up a material and want to use the textures again for anything else, how do I access them?
They are not available in the shelf anymore after restarting the tool.

Thank you,
Sekuta

[Jeremie Noguer]

You can right click in an empty part of the material properties when a fill layer is selected. This will allow you to save that material in ths ehlf.