Pages Field - defining selectable

Is it possible with the Pages Field to specify that only grandchildren (or whatever level) are selectable? I get the full tree as I need but it’s still possible to select the children (eg ‘categories’) when really I just want this level to be navigable only and pages on the next level down to be selectable.

Yes, the pages field accepts a query, so for example you can filter page.grandchildren

Thank you – yes, there is that, but then you loose the ability to navigate by the child layer – all the grandchildren get lumped together. My question is that is there a way to still display the child layer but only select the grandchildren.
This isn’t it but something like:

  type: pages
  query: children
  selectonly: grandchildren

I see what you mean, but no, this is not possible out of the box. You could create a custom implementation of this field.