no lasso tool in xara; that's a different concept; the scribble is a close as you get

[although if you are really good with the marquee select in 'adobe' mode you can build up a selection with the help of the shift key quicker that you might in normal xara mode; it depends what you are trying to do

'adobe' mode': marquee only has to cross part of an object to select
'normal' xara mode: marquee has to totally enclose the object to select

shift key toggles add/subtract to selection as normal]