Assuming that your current period is December or Q4, you can use sets for what you want!
1. Create a set for displaying the current period in the below chart. Values in the set: Since you have 2 date formats - month & quarters, you have to select December first, then change the parameter to quarters and then select Q4. Let's name this set as 'Current Period'.
2. Create another set and do not select any values. It's going to be an empty set and let's call it 'Selected Period'.
3. Select these two sets and create a combined set. Let's name it accordingly. In the combined set, select all members in both sets.
4. Add this combined set to the Profit vs Sales sheet as a filter.
5. On the dashboard, remove your filter action and create set values action.
6. Create the above set action as below. So, when a month on Sales by Market sheet is selected, that month value is passed into the 'Selected Period' set that we created earlier which in turn updated the combined set. Make sure that you select "Remove all values from set" at the bottom to ensure that the sheet at the bottom switches back to current only once you deselect.
7. Now that should do the trick. However, if the user clicks on the market instead of the single month, all the months are selected which means all the months are displayed in the below chart. If you don't want this to happen, just place a floating blank object over the market values which would not let a user click it.
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