I will show you how to add a button to a repeating table and be able to copy information from that row to other fields.
Create a list in SharePoint and name it Location with three columns, Title, Region and City.
Add a data connection to your form to receive information from this list in SharePoint. Now when you have your repeating table as a secondary source, highlight it and drag it to your form.
Put your cursor somewhere in the column for ID, right click and choose Delete – Columns, now you only have the Title, Region and City columns left.
Now put the cursor somewhere in the City column, right click and choose Insert – Columns to the right.
It should now look like this
Now add a button in the field next to the City field.
Add three Text Box fields somewhere in your form and name them MyTitle, MyRegion and MyCity.
Highlight the button and click Manage Rules in the ribbon. Create a new Action rule to set a field’s value. It should look like this.
The Value is built by adding the function current(), then a slash “/” and lastly, add the field Title from your secondary source Location.
Repeat this step twice so that you get a value for each of your three fields. You should now have three actions in your rule, like this.
That’s it, this is how it could look.