BrickLink: Sell items as whole set and/or individual parts
The specific feature you're asking doesn't exist. However, you can make notes on your set listings and say that you're willing to part out the set.
In addition, there are sophisticated tools for buyers to create wanted lists and check which sellers have all or most of the parts they need. So, if for example, they are looking for several parts from the same set, sellers who have those parts will automatically show up for them. Sellers don't have to do anything extra besides listing the parts to have this feature active.
Based on my personal experience as a BrickLink seller, my suggestion would be to list the sets you have for a few months (sets sell well during the Christmas season, so you may want to list it until the end of the year). Then, if they doesn't sell, part them out and sell the parts individually.
Also, consider listing the sets on eBay. In general, sets sell quicker and for more than on eBay. eBay buyers are more casual LEGO fans and are usually looking for gift items, sets from their childhood, etc.. BrickLink buyers are more project-focused, and they are looking for specific parts for their custom projects and not whole sets.