This is easy. Doesn't matter if the {{Lead.URL Field}} value can be wildly different URLs, you don't need to reference the token value in the trigger. Constrain the Clicks Link in Email trigger by Link ID. Then just give the link an ID, like <A id="lead-url" href=...>.
which you could also tokenize...
Sure, though it might be easier to use the name of the token as the id, like id="URL-Field".
Ah, good point. So technically you can't use the dynamic URL as a trigger directly but that's a nice workaround!