You can’t/shouldn’t leave. You can’t get your marriage extension in time. So the advice is to get either a visiting family or Covid extension. Great advice.
But, after this extension, you still have a valid multiple entry, unexpired visa. You have a choice then approaching the end of your family/covid extension. You can extend it. Or, you can leave the country, do a ‘border bounce’ and come back on another 90 stamp on your original Multiple Entry visa up to its expiry date.
Obviously this is only useful if the border restrictions are loosened, or if you don’t have the funds to extend in country.
I did this years ago. Multiple entry visa, got a job, an annual extension. 6 months later I quit my job. Cancelled my extension and then just left and came back in on my original visa. Did 3 more border bounces on my original visa, including one on the very last days before it expired for another 90 days.