I assume you currently have a value assigned to Default Time. The procedure should be:
- Assign that value to the first period of the first year, creating a Stored Item. You do that by selecting the first period on the tree in the left-side of the pop-up that appears when you double-click on the Text property and entering a value.
- Assign a new value, which can be anything, to 2022M6, in order to create another Stored Item.
- Edit that second Stored Item and delete the placeholder value. DO NOT use the "Remove Stored Item" button.
This should ensure that all past periods get a derived value that is the old text, and all periods from 2022M6 forward get a blank derived value.