I've just set up a Column, Statistic and Report to test this, but I don't think that the database field for 'has position' is working correctly.
I'll give the walkthrough of what you need to do, though, so that you can understand how to create statistics and reports.
1. Open the configure stats window. Configure -> Configure Stats.
2. The stat we want to build relates to each hand, so choose section "Holdem Cash Hand".
3. Click the 'Columns' tab.
4. The 'Edit Column Info' fields on the right should be empty, but if they aren't click "New".
4a. Enter a name for your new Column - the naming convention name would be "flg_f_has_position", but you can call it what you like.
5. Click "Insert" by the Expression field.
6. Select "holdem_hand_player_detail" Table Name (we want detail about how the player played a hand).
7. On the right, select "flg_f_has_position" - you can click the 'Field Name' column header to sort alphabetically.
8. Click OK.
9. Back on the configure stats window enter a Description (just some text) and click 'Save'. You now have a Column.
10. Click the 'Statistics' tab, again, the fields should be empty, but click New if not.
11. Enter a name for your Stat, e.g. "In Position Flop".
12. Enter a Description (just text).
13. In the Value Expression, click 'Insert'.
14. On the Columns tab, choose the column we just created - flg_f_has_position or whatever you called it.
15. Click the Format tab.
16. Enter a title (e.g. "Flop In Pos") and a width to be used in reports (e.g. 65).
17. In the Format Expression field enter..
format_bool( flg_f_has_position, 'check')
This means that the stat will be shown in reports as a checkbox, checked if true. (You can 'build' this expression by clicking Insert / Functions / Format Bool / OK, then highlighting "value" and Insert / Columns / flg_f_has_position, and changing 'format' to 'check'.)
You can leave Format Summary blank for this stat.
18. Click 'Save' then 'Apply' to store your new stat and close the config window.
19. On the 'Texas Holdem' tab, click 'Reports' tab.
20. Set the 'Section' to 'Holdem Cash Hand'.
21. Bottom left, enter a name for your report.
22. In the Available Stats list double click 'Hand #' and then your new stat's name ("In Position Flop") to add them both to the Report.
23. You can now run the report and you should get 2 columns showing you all your hands and whether you were in position on the flop.
Problems with this Stat/Report.
I think there are problems with using Simple Filters with this stat, and also a problem with the value of the stat (or underlying database field) which I will create support tickets for.
..but hopefully this will explain how to create stats.
The best way to learn is to look at how some existing stats are constructed and adapt that to your own uses.