知ってて

knowing (that), knowing and

→ 知る
知っ to know + て Te-form (conjunctive form) + て Te-form (conjunctive form)
verb · informal Rare #32,348
knowing (that), knowing and Colloquial contraction of 知っていて.
JA: それを知ってて、黙っていた。
EN: Knowing that, I kept quiet.
Conjugation of 知る

質問があるんだ何か知っててここへ来たのか?

I have a question. Did you come here because you know something?

— サイコ (1960)

知ってて冗談言った

I knew, but I was just joking.

— 最強のふたり (2011)

ベルスはお前が戻ると知っててやったんだ

Bels did it knowing you’d come back.

— es[エス] (2001)

知ってても言うか!

Even if I knew, like I’d tell you!

— Sanjuro (1962)

知っててほしいことのひとつだよ

It's one of the things I want you to know.

— ドライヴ (2011)