Hi Gabriel,
Thank you very much for your answer!
Here below I describe my progress/findings/problems.
Apologies if it is a bit long, but I find that being detailed in what you describe helps reducing the going back and forth.
Please keep in mind that I might be doing some things wrong, so please you are very welcome to correct anything you see fit.
Before that, I wanted to tell you that I installed and spent a while looking at the Tasks application, and it might not seem so, but it is a really complex application to reverse engineer for a newbie in REI3, like me, so I find it very unlikely that I could learn many things from these complex examples, at this time at least.
I think that in order to be able to understand all the architecture, hidden logic and behavior (that is distributed at many different levels), and many others things present in the application you need far more knowledge of the platform than what you can get from the documentation.
And please do not get me wrong, the documentation is pretty good as a reference, but it does not show/teach how to think ,or the mind flow/set you need, in order to go in the right direction when trying to do things.
I'll really appreciate your comments on this, and on the specific problems I found in order to build what I was trying to build.
Thank you very much!!
Warm regards!!
Ricardo
From here one are the specific things I'm working on, and in which I've found some problems I couldn't figure out.
To be able to select a Form in the Open Form section, the Form itself has to be related to the relation at Form level to one relation, for example : estandar
If I don’t do this I don’t see the Form in the Open Form section.

Now, for the list of estandar I have to link again to the estandar relation in order to be able to display fields.


First “problem”, I get duplicated New/Save buttons, and the Form level ones are grayed out. Of course I unset the relation at Form level the buttons disappear, but I become unable to select the Form in the Open Form section.

Now I add the estandar_seccion list.

And I get this: which is logical (first list=all the estandar records, second list all the estandar_seccion records)

So far so good. But here is where I have to admit I get lost.
The two lists are unrelated so far, so if I click one estandar record the same Form opens showing exactly the same information, and what I want to achieve is just a refresh of the estandar_seccion list to show only the records associated to the estandar record selected.
Of course, as you said there is no field in the form to filter the second list, as list fields from the first lists cannot be used as filters. So I’m starting to think that what I want to do is not possible, at least not the way I’d like to.
So, if I change my UI behavior to what you suggested, opening another form, I get to this point:
I have this form that lists the estandar records. No relation at Form level:

However for the list I HAVE TO use these 2 relations. I bit later I’ll explain why I had to (but I’m aware that maybe I’m doing something wrong)

Which leads me to this result: getting one estandar record for each estandar_seccion related to that standard in the output
Here is the SQL
SELECT "r0"."nombre" AS "e0", "_r0"."id" AS r0id, "r1"."id" AS r1id
FROM "desarrollo_sostenible"."estandar" AS "r0"
LEFT JOIN "desarrollo_sostenible"."estandar_seccion" AS "r1" ON "r1"."id_estandar" = "_r0"."id"
However I cannot edit the SQL for doing something like grouping the records by _r0id.
What would be the right way to group or add complexity to the SQL inside REI3?
Second "problem" to solve: how to show only one estandar record per existing estandar?

When I click on any of the records I open another form that shows like this: which is fine.

This is the form definition:


