Custom AppFeatureBlock actions absent from automation builder action picker — all triggers, all configurations tested

Two custom AppFeatureBlock features in app 18756 v13 do not appear in the from-scratch action picker, regardless of trigger.

Account / app

• Account: pageproof-force (6802012)
• App id: 18756, v13 draft (versionId 15461381)
• Affected block keys: block_create_item_and_keep_in_sync_671900, block_keep_item_in_sync_671901

Symptoms

Both blocks are invisible in the "Then do this" action picker when the trigger is set to any of: When status changes, When item is created, When subitem is created (all monday-builtin), or PageProof's proof_reaches_status, proof_created_or_updated, proof_updated, proof_updated_with_subitem_reference. Sibling blocks in the same app appear normally (e.g. block_sync_subitem_671790, block_create_proofs_for_assets_in_column_671797).

What we've verified

• mapps manifest:export -i 15461381 returns exactly what we imported — monday's stored copy is correct.
• The affected blocks have identical structural patterns to working sibling block_sync_subitem_671790: same inboundFieldsConfig.fields[].type and fieldTypeReferenceId, same constraints.subFieldsDependencies, same outboundFieldsConfig, same executionConfig, same lite_builder.sourceConfig shape, matching sentence.
• Trigger output names match action inbound names (e.g. proofItemMapping on both sides).
• Tested in an incognito window — same result.
• Multiple manifest re-imports — same result.
• Deleted both blocks and their three referencing AppFeatureWorkflowTemplate features (automations_template_30811600/601/602) from monday, then re-imported via mapps manifest:import — recreated, still invisible.
• Stripped migrationEntityId and migrationId from the affected blocks, then deleted + re-imported again so they were created with no migration lineage — still invisible.

Hypothesis

The blocks were originally added via the Developer Center UI post-migration (migrationEntityIds 28201/28202, outside the range of the wizard-created blocks 28096–28107). We suspect a registration path that doesn't fully wire the block into the new automation builder's block index. The recreate + strip-migration-markers experiment did not change behavior, so there may be additional account-scoped or app-scoped state we can't see or reset.

Ask

What additional registration step or metadata is required to make a custom AppFeatureBlock (kind=action) appear in the from-scratch action picker? Is there a way to force re-indexing of specific blocks?