How to set 3 levels of hierarchy in the Schema ?

As in post https://openforis.support/questions/497/collect-survey-designer-parent-code I would like to link 3 levels of plots (parcelle,carré,quadrat ; then trees) with 3 neested 'Code Attribute'. Those levels are well defined in the sampling_desgin (level_1 -> level_3).

level1_code level2_code level3_code x   y   srs_id  province    region  plot_id 
1   1   1   100 1800    EPSG:32630          1_1_1
1   1   2   100 1800    EPSG:32630          1_1_2 
1   1   3   100 1800    EPSG:32630          1_1_3
1   1   4   100 1820    EPSG:32630          1_1_4

I can set the level_2 for 'carré' with his parent 'parcelle'. But I can't set the level_3 for 'quadrat' as the "Select parent attribute" popup only shows the level_1 'parcelle', not the level_2.

How can I set this level_3 ?

Btw I can specify (I tested that works) the geofence of a tree with the coordinates x,y with the formula : idm:samplingPointCoordinate(parent()/parc_id,parent()/carre_id,parent()/quadrat_id)