Trendline for each Cluster Series

I think you will need to calculated the data for the trendlines in the spreadsheet, then build the chart as a clustered column + XY scatter combination chart. Spend some time with this tutorial to see how the chart is created: https://peltiertech.com/clustered-co...ination-chart/

If you are unsure how to calculate the trend data, I would probably use the TREND() or FORECAST.LINEAR() function: https://support.microsoft.com/en-us/...3-9a7cf7b51ef1

Perhaps I am misunderstanding then, because it looked like it should be readily adaptable to the picture you included in your sample file. The overall procedure I would expect:

1) Calculate trend values in the spreadsheet.
2) Enter/Calculate horizontal position values to go with the trend values. The only difference I see is that Peltier's example chose position values for trends across categories where you want position values for trends within a category. Is where you are having trouble understanding how to adapt Peltier's tutorial to your situation?
3) Create and format the column + scatter combination chart. This should be straightforward once step (2) is completed.

Let me know what I am misunderstanding.

I'm not sure what you have tried. Here's what I did:

1) In A2:A5, enter 1,2,3,4, to represent the desired X values for the trendline regression.
2) In C11, I enter the trendline formula =TREND(B$2:B$5,$A$2:$A$5,$A2). Note the mix of relative and absolute references and Copy/paste/fill into C11:F14.
3) Select D11:D14 -> Cut/paste/move into C16:C19. Select E11:E14 -> Cut/paste/move into C21:C24. Select F11:F14 -> Cut/paste/move into C26:C29 This column will become the values for the trendlines in the chart.
4) Select B1:F5 and insert a clustered column chart.
5) Bring up the "Select Data" dialog, add a data series using C11:C29 as the values. Dismiss Select Data dialog.
6) Select this new series and change chart type to XY scatter (markers with lines is indicated in your picture).
7) Bring up the "Select Data" dialog again, select the trends data series, and Edit the series to use B11:B29 for the X values.
8) Start entering values in B11:B29 until you find good values to position the trend points where you want them. I started with 0.25 to 1 in B11:B14, then adjusted from there (ended up with about 0.7 to 1.2). From there, the subsequent quarterly groupings appeared to be 1 unit to the right (so B11+1 copied down).

Try that and see how close you get to what you want.

I won't be able to work on your file until some time tomorrow. Until then, is there a specific step that you are having trouble following?

I still have no idea what step you had trouble with. Here's what I ended up with. The values in B11:B14 still need some adjustment to get the right horizontal position.

I did not calculate those values. I just guessed them. They aren't perfect, so feel free to adjust them to get better horizontal positions. I usually prefer to just hand enter different guesses until I get something I'm happy with. If you feel they must be calculated, I will refer you again to Peltier's tutorial where he describes in some detail how Excel correlates the XY scatter horizontal axis against the category axis of the column chart.