Adding Animation & Rigging as blocking reviewer, as per our experimental code review guidelines.

The animdata_filter_ds_modifiers() function already loops over animation data from modifiers. Wouldn't it be possible to extend animfilter_modifier_idpoin_cb() (used by animdata_filter_ds_modifiers()) to handle node trees?

In D10309#258979, @Sybren A. Stüvel (sybren) wrote:

The animdata_filter_ds_modifiers() function already loops over animation data from modifiers. Wouldn't it be possible to extend animfilter_modifier_idpoin_cb() (used by animdata_filter_ds_modifiers()) to handle node trees?

BKE_modifiers_foreach_ID_link / animfilter_modifier_idpoin_cb is just for IDs referenced in modifiers (e.g. textures), see the comment above animdata_filter_ds_modifiers

we could consider including that animdata for geonodetrees as well, but I would still think this needs to be separated from animdata_filter_ds_modifiers

In D10309#258983, @Philipp Oeser (lichtwerk) wrote:

animfilter_modifier_idpoin_cb is just for IDs referenced in modifiers (e.g. textures), see the comment above animdata_filter_ds_modifiers

In what way is a bNodeTree not an ID referenced in a modifier?

In D10309#258990, @Sybren A. Stüvel (sybren) wrote:

In D10309#258983, @Philipp Oeser (lichtwerk) wrote:

animfilter_modifier_idpoin_cb is just for IDs referenced in modifiers (e.g. textures), see the comment above animdata_filter_ds_modifiers

In what way is a bNodeTree not an ID referenced in a modifier?

afaict, it is only for IDs in node properties, see foreachIDLink in MOD_nodes.cc

I still don't understand what you mean. This patch seems to work fine on the test file from T85356:

diff --git a/source/blender/editors/animation/anim_filter.c b/source/blender/editors/animation/anim_filter.c
index f2022194ed5..a03f19d0111 100644
--- a/source/blender/editors/animation/anim_filter.c
+++ b/source/blender/editors/animation/anim_filter.c
@@ -2403,6 +2403,13 @@ static void animfilter_modifier_idpoin_cb(void *afm_ptr,
       }
       break;
     }
+    case ID_NT: {
+      bNodeTree *node_tree = (bNodeTree *)id;
+      if (!(afm->ads->filterflag & ADS_FILTER_NONTREE)) {
+        afm->items += animdata_filter_ds_nodetree(
+            afm->ac, &afm->tmp_data, afm->ads, owner_id, node_tree, afm->filter_mode);
+      }
+    }
 
     /* TODO: images? */
     default:

This approach extends the existing structure that loops over all modifiers and follows ID pointers. Extending it further when necessary is then just a matter of adding another case to the switch.