What is the correct, common usage?
Can effortful be used in a complimentary way or does it more closely align with words like laboured that often, (but not always) have neutral or negative connotations.
It has a terrible connotation: that the writer is using a vague neologism instead of searching for a more specific synonym.
If you want to praise the subject for the amount of effort, use diligent. If you intend to highlight the difficulty of the task, use laborious.
If you are not the writer but the reader, find a better writer to read.
A Google Ngram suggests the word has no common usage as it is fairly new in printed works. Use to the word in contexts seem to indicate specific special uses, as in the very specific "Effortful Control" .
I would be very careful in using the word. Which is to say, I probably would not use it.