In order to accomplish that you must create an unfiltered table list, where genio does not make mandatory the tables to be related, and you can put the columns that you intend to use.

After you need to create a manual control (manwin) to filtre the table list, because if you publish you'll see as the name hints all the records on the database table.

The manwin is quite simple. As you can see in my example. The type is OVERRQ  and parameter is the name of your Form followed by "_" and the name of the Unfiltered table list itself.

As for the code, is just a line similar to the one I show below, where you indicate the conditions to limit the table by the key of the form's table.

Seeing it by parts:

1 . "autob___pseudautautod"

        - Identification of the unfiltered table list again but attention that now following the forms name there must be underscores to make 8 characters, followed by the table list name

2. "Conds.Equal"

        - comand to compare and show the equal ones

3. "(CSGenioAaucon.FldCodautod"

         - table related field of the area present on the table, attention the A is for Area is always needed and in caps  (in your case must be CSGenioApeca1.FldCodclien2)

4. "Navigation.GetStrValue("autob"));"

         - here you say where the application gets the key, in this case the form in use through the navigation (in your case Clien1)

Attention: This is possible without manual code. Please try the following solution.

Create an area of PECA1, for example PECAX, and put a relation for CLIE1 and CLIE2 in PECAX but exchanged in relation to what is in PECA1.

Then just create a PECAX table list in the CLIE1 form.

This is what I got, the second table bellow should be only the supplied pieces but instead it shows all the available pieces.