With paint.net, Gimp or any other software to edit textures have keyboard shortcuts like P for the pencil with paint.net. And it will be nice to have few shortcuts for the texture editor too.
Issue comments
Also can there be a button that you can press to open up your desired textur editor for example I can select a texture editor like paint.net and when ever I want a new texture I click the button to open it up and make the texture and the texture will be saved in the workspace
and when editing a pre-existing one it opens the desired texture editor
I will forward this to Matej ;)