Ultimately it's up to you, and it's best to decide on medication changes with your psychiatrist. But if want opinions from other bipolar patients, my opinion is that one day only is way too short of a trial to warrant stopping a new combo, unless it lands you in the hospital or is disturbing to a very very great level. What you describe sounds quite disconcerting, but it sounds like the dream may be the only cause. Nothing says that your new combo will permanently cause disturbing dream issues. There certainly are "one-offs" or even "three or more-offs" that don't mean the situation is permanent. Again, it's up to you.

As bipolar patients go, I'm a very tolerant one. Sometimes I've been too tolerant, but other times my patience and tolerance served me well.

I have no experience with taking Lexapro with Seroquel. I did take Lexapro maybe 15 years back, and didn't have dream issues. All I remember is that it gave me night sweats and eventually caused manic symptoms. I wasn't on a moodstabilizer or antipsychotic at that time.

Seroquel is sedating and I imagine could effect sleep in various ways. Though 100 mg wouldn't be a large dose for me (I take 550 mg), it is still sedating, especially if you are not manic at the time. Even if manic, it might affect REM sleep, but likely not permanently for most.

I had a scary dream last night. But I usually don't.