Hi,

I'm trying to configure my itemization environment so that second level switches to a smaller font.

Sorry I cannot help you here.

I imagine I'm doing something wrong but could not figure what ... (setupitemize[1][before=\tx] is works well)

the before= after= and between= seem to be only for tuning the spacing. And they seem to be used only when you play with \autoitemgroupspacing (see core-itm.tex for details). The before=, after=.. are grouped, so no fontswitch will take effect for the text. I wonder why. And I wonder if this is documented somewhere. Patrick