So my parents got scammed last night, fraud case is open but it's likely not gonna go anywhere and they'll be out 10K - they know better and now they really know better, and I'm hoping to get some advice on a repayment strategy.

They absolutely don't have that kind of money and repayment will take a while.

Plan one is just put it on the mortgage, but they're currently locked in at a lower rate for 2 more years, so adjusting that isn't ideal if it changes the rate. If not, adding 10K to mortgage is no brainer.

Line of credit does carry lower interests, but it will accrue daily, credit cards are high interest, but interest is racked up monthly.

Would it be possible/smart (assuming +10K credit card capacity) to move LoC debt to the credit card for 25 ish days a month to avoid daily LoC interest, and then send the debt back to LoC for 5ish days (transfer time) and have the credit card at $0 at the end of every month? No credit card interest and far less days for LoC debt to accrue interest?

Obviously there is risk in not having the credit card paid off in time, but would this strategy be viable if properly executed?