Short version: whilst trying to build a custom action that involves several "glue items" commands, in reality after runnung the action Reaper will "glue items" for the first time and skip the second "glueing".
Longer version: I'm trying to compile a custom action that would "render" a master mix and then prepare it after two diferent loudness specs. Here's where I am now:
1. Render time selection + import rendered file into new track
2. Normalize loudness to -23LUFS
3. Glue items
4. Normalize loudness to... (after normalizing Reaper leaves the item unglued)
3. Glue items