If you have already input the data for them as joint, there is a "Split MFJ return" option under the FILE menu. This will split them. As long as you have the MFS indicators on, it will assign the proper deductions to each spouse. Of course, if you have already entered them separately, just mark the MFS box in the filing status. There is also a MFS "what-if" worksheet that will tell you what you are going to get, once you split the return, this way, you can make adjustments before you split.

In my experience, most couples who have equal income above $50-60k with no children or tax credits to claim, benefit from MFS. It's less since 2018 because the standard deduction is so high, but generally the tax bracket alone is enough to justify MFS.