@StuPower
Actually, you might be overcomplicating things for yourself a bit.
The first formula actually does work and works fine.
Patch('Objective Setting_1',Defaults('Objective Setting_1'),{Links to strategy:ComboBox.SelectedItems}
So, if that is not working for you, then I'd suggest getting to the root cause of that problem rather than create another method to work around it. That will just bring you more grief.
If the above is not working, then there are at least two things to look at first:
1) The definition of your column. This is most important. Are we looking at a Choice column (I assume) and what kind of parameters are set for it? Does it allow multi-select? Does it allow add-in choices? (Are you trying to add in choices? ) Does it have any other conditions to it?
2) The Items of your ComboBox - they should be a table of Value records...that is all you need for the above to work. Best choice is the Choices function as it was designed to give you the viable choices for a column If you are doing anything different (such as Distinct or filter or other) you will need to pre-shape the items data into a table of Value records.
Based on those two observations, you should be able to get to the root cause of why your patch statement doesn't work.
BUT...the point being - that patch statement should work fine if the proper conditions are set up for it.