What exactly do you want to do? This is a situation where you should be asking what you're trying to do, rather than how you're planning to do it.

IIRC, Lestrade's stops auto-syncing with Steam if you're inactive (i.e. haven't logged into LT's for at least a week.)

I simply don't want to sync my lestrade wishlist with the steam one automatically
I have to manually remove some of those titles every time it sync cause I'm not looking for trade some of them
Should I use blacklist?
Is not more reasonable to be able to manage it manually?

Hence my question.

The solution is to select all items you want to ignore in your wishlist page, then either set the items' quantity to zero, or tag them with 'no offers'. The former will hide them from matches, the latter will show them, but you'll be the only one who can add them to an offer.

Simple ;)