How do i know witch IAL is being used by a lobby element?

It’s hidden away in the PRES_OBJECT and PRES_OBJECT_DEPENDENCY views.

You can filter PRES_OBJECT by object type to get the lobby elements and then use PRES_OBJECT_DEPENDENCY to get the related lobby data source.

Then it gets messy as the view with the data source definition COMPOSITE_PAGE_DATA_SOURCE holds the information you want in CLOBs as XML 

Something like this might work…

select xt.*

from   PRES_OBJECT po
inner  join COMPOSITE_PAGE_DATA_SOURCE cds
on     cds.id = substr(po.po_id, 16),
 XMLTable('for $i in $XML/SQLDataSource
           return element result {
              for $j in $i/Select/DataColumn
                    for $k at $pos in $j/Column
                      return element row {
                             $i/Name,
                             $i/ID,
                             $i/View,
                             $i/Where,
                             $j/Column[$pos]

                     }
                 }/row
          ' PASSING xmltype(cds.value) as "XML" COLUMNS
                XName varchar2(50) Path 'Name',
                XID varchar2(50) Path 'ID',
                
                XColumn varchar2(50) Path 'Column',
                XView varchar2(50) Path 'View',
                XWhere varchar2(50) Path 'Where'
                ) xt

where  po.po_id like 'lobbyDataSource%'