Hi Henri,
a) the "analysis" engine (I assume you mean the engine for the PicoTutor) has nothing to do with the stockfish engine in the web browser provided by the picochess web server. the stockfish engine of the web browser is a java engine (I think) and runs locally on your device where you use a web browser to access the web server.
b) in the web browser which runs on the same device as picochess the number of analysis lines is fixed and set set to 1 because (if I remember correctly by Gerhard) because of problems when activating/running multiple lines in the chromium browser.
If you start the analysis on a different (external) device you will be able to activate multiple lines
Dirk