I could be doing

Amir OghlowIs "I could be doing" here to draw a conclusion

No. could signals possibility or ability here.

The sentence is a little unusual. I didn't expect a mix of present and past.

I honestly don't know what else I could be doing. (present)
I honestly didn't know what else I could have been doing. (past)

C

I honestly don't know what else I could be doing.
Does it have the same meaning as I honestly don't know what else I can do or I can be doing?
Are both correct?

Amir OghlowI honestly don't know what else I could be doing.Does it have the same meaning as I honestly don't know what else I can do or I can be doing?Are both correct?

Yes. That's the idea. Both are correct.

CJ

What about this?
I honestly don't know what else I could do?
And why did they use ing?

Is "ing" used to express something happens now?
For example, She could be living in Spain.

Amir OghlowIs "ing" used to express something happens now?

Yes, and the activity continues over an indefinite period of time.

She might be living in Spain.
She might live in Spain.
Is there difference?

Amir OghlowIs there difference?

A: Do you know where Francis is now?
B: She might be living in Spain. (This is the most common answer. )

"Might live" is general, without a specific time reference:
Intelligent life might live on other planets in the galaxy.
When children get married, they might live in the same city as their parents.

Okay,
"I honestly don't know what else I could be doing."
I really don't know why they used "ing"?
And is it correct to say "I honestly don't know what else I could do."?

Thank you very much in advance.

Amir Oghlow"I honestly don't know what else I could be doing."

The -ing is used to express an activity that continues over time.

Suppose my job is cleaning bathrooms in an office building at night.
This job pays very little money. What else could I be doing to have a better life?
Answers:
I could be going to school, studying to b