Re: Custom layout : how can Lyx transfer parameters to LATEX ?
Here is the answer :
For this, you need to go to the (beta as for now) LyX 2.1.
For details, go to the Customization (Personnalisation en français) help document and see paragraph 5.3.6 the new portion regarding the "Argument" section.
You can enter the parameters through new items that appears in the menu (Insertion en français). The parameter then appears in your text in red (like TeX additions) under the name you gave to the parameter (through the LabelString specification).
In the Latex portion of the .layout format file, you can then use the arguments defined by using the syntax #1, #2 etc.