Custom Actions can be replaced without warning

[ES-Alexander]

Bug description

Custom Actions are apparently registered by name, so if you create one with a name matching an existing one then it (silently!) replaces the old one:

Screen.Recording.2025-02-07.at.3.14.46.am.mov

Steps to reproduce

1. Create a Custom Action
2. Create another one with the same name and type, but different features
3. On save, only the new one exists (the old one has been replaced)

Primary pain point(s)

It's unexpected for a name conflict to cause an instance replacement without warning.

Ideally choosing an existing name when it is in use elsewhere should be treated as invalid input, with a warning like "Action names must be unique - please choose a different one."

Additional context

No response

Prerequisites

• I have checked to make sure that a similar request has not already been filed or fixed.