Finding Where Templates Are Stored

Here are some more "advanced" approaches you can use, in a business setting.

This is an advanced approach, but does not require addons. You combine PowerBI with a PowerApp and online database to store the comment data.
How to Implement Writeback Comments in Power BI Using Power Apps

https://zebrabi.com/writeback-comments-power-bi/

In this post, we'll look at how you can add dynamic writeback comments to your dashboards with Power Apps, allowing users not just to add dynamic comments but also to write back their feedback directly in Power BI. This will require you to have a Microsoft account for using Power Apps.

The number one question we get when doing our webinars is: “Can you talk more about this option of writing the comments back from Power BI?” We heard you and today we’ll explain how you can use Power Apps to do writeback comments in Power BI.

This is a step-by-step tutorial to demonstrate the whole process from a blank Power BI report to a fully functioning solution of write-back commentary.



PowerBI:
An "advanced" solution is to add comments to a PowerBI, which includes PivotCharts which is only supported by "Business" versions of PowerBI

Add comments to a dashboard or report

https://learn.microsoft.com/en-us/power-bi/consumer/end-user-comment

APPLIES TO:
Y: Power BI service for business users
N: Power BI service for designers & developers
N: Power BI Desktop
Y: Requires Pro or Premium license

Add a personal comment or start a conversation about a dashboard or report with your colleagues. The comment feature is just one of the ways a business user can collaborate with others.


There is also an addon tool called "Zebra BI". It includes a feature to add comments to specific data

Zebra BI defines an internationally used reporting standard. One of the elements of that standard includes "dynamic comments"
Actionable Reporting Manifesto: What it is and why we need it? – Zebra BI- 2022 06 16

https://www.youtube.com/watch?v=mCcRkkwogM4 14min

The new reality calls for short action distance.

However, digital transformation can't happen without the adoption by the entire organization.
We present you THE ACTIONABLE REPORTING MANIFESTO.
#5 Add Comments

Comments should add quantitative information to qualitative information. This adds value to reports.

These days it is expected that these coments are dynamic.

If the user clicks on a filter, the comments change to explain the right data categories, directly on the visual, interactively. (Change from P&L to Balance Sheet)

Another addon that includes a comment feature is called InfoRiver
https://inforiver.com/commenting-powerbi/

A slightly different approach can achieve similar effect, without having the captions as additional range in the sheet.
1. Just create your graph with data labels inserted, as per the tip. For the time being, leave one of the choices Value/Category Name/Series name checked , but make sure that the Value from Cells is unchecked (important).
2. Now you can select a Data Label in which you want to put a custom caption (click once on any Data Label, then again on the label you want to modify). Click again on this label to select the text content of this label. Type in your custom caption, overwriting the selected text.
3. Repeat this for all other data labels you want to modify.
4. Once this is complete, in the Format Data Labels panel uncheck the option for Value/Category Name/Series that you left checked in step 1.

After that, only the modified data labels should be visible. You can format each of them individually, as I described in my earlier comment. You can use Show Leader Lines option, and format them as I described in that earlier comment. Alternatively you can use change the shape of the data labels to callouts (also described in my earlier comment).
Examples of this approach: (see Figure 1 below) (see Figure 2 below)

Once you have your Data Labels set up as per this tip, for more impact you can format the data labels. I suggest to format each of them individually, otherwise the empty labels may show up as placeholders:
- change fill colour/pattern, and border colour/thickness.
- Change size and colour of the font.
- resize the data label.
- data labels can be rotated from -90 to +90°, which may allow to organize them easier and avoid overlapping.
- Instead of using leader lines, you can change the shape of any Data Label to one of the callout shapes (right click on the selected label and chose Change Data Label Shape. Initially, the callouts point to the proper data point, but that can be dragged to another point. However, doing so may cause that pointer to mis-behave when the chart is re-scaled.

You can also add line breaks within the cell with captions. If they are manual line breaks (Alt+<ENTER>) they will be reflected in the Data Label, while wrap text setting will not.

For even more impact, you can change format of individual data points (click the series, then click again on the point (column, bar, point, etc) you want to modify to select it.

If you Show Leader lines you can format those too, but the format applies to all of them. You can select line colour and thickness and the arrow type and size. The beginning arrow is the one that points to the data point. (see Figure 1 below)