Hi Marcelo

Thanks for posting on the community! Recently Lucidchart updated its user interface to present a cleaner simpler workspace and only show you the tools you need when you need them. Due to this it is no longer possible to fix the layers panel on the right bar. 

However if you would like to see this feature again in the future please add your idea to our feature request form? Ideas submitted to this form are passed on to the product development team for their consideration.

In the meantime you can manually open the layers panel in the bottom right corner of the editor and move the layers panel to the location of your liking. Then as you continue to work in the document you can open and close the panel and it will remain in its chosen place (see gif below).

For more information about layers take a look at the Layers article in our Help Center.

Hope this helps!