Duran, o cümle geçmiş zamanda nasıl yazar? (It seemed to me that she knew everything.)
"Ki" kelimesi koruyabilir mi?

I couldn't catch what you mean? Sorry.

Duran, you translated the English sentence:

==> It seems to me that she knows everything.

as:

==> Bana öyle geliyor ki o her şeyi biliyor.

How would you translate the sentence in the PAST tense?

==> It seemed to me that she knew everything.

Can the word "ki" be retained in the Turkish sentence when it is in the past tense?

In fact, it is usually used in simple present tense. There are a lot of sentences.
You can use "ki" in simple past.

It seems to me that I heard a noise in the attic.

Duran, OK, let me try this again... :-)

How would you translate the sentence in the PAST tense?

==> It seemed to me that she knew everything.

Bana öyle geliyordu ki o her şeyi biliyordu. [Correct?]

==> It seemed to me that she knew everything.

Bana öyle geliyordu ki o her şeyi biliyordu. [Correct?]

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If you make both sentences past, then you have to do the same in Turkish.

Bana öyle geldi ki o her şeyi biliyordu. (I don't always hear a sentence like that; thus, it may not sound natural)

Here "ki" means "that"
It has nothing to do with the tense.

Bana o her şeyi biliyor gibi geldi. (Past) or as Gulo said, Bana öyle geldi ki o her şeyi biliyordu.

Thanks.

Don't mention it DOSTum:)