There is a "chicken and egg" type situation that comes up while the developers are creating new brush engines for Krita. This ticket is to come up with a clear and simple way on how to solve this dilemma.
Once a preset is created for a new brush engine this is not an issue. To clarify...this situation mostly applies to developers, not artists.
From what I know, this is currently what is done in this situation.
When a new brush engine is created in code, there is no process for generating the first brush preset
3.0 process for generating the first brush preset
In 3.x, the work-around is to use the application's (Krita) GUI brush editor to do this. If you change a brush engine, it 'disconnects' the currently selected brush from the editor and changes the settings area to the new engine. From here, a developer can save the brush preset as the new engine type.
4.0 process for generating the first brush preset
In 4.0, this behavior was changed so that you cannot have a "disconnected editor" from your brush. The brush engine drop-down is a filter that filters out brush presets from the full list. It does not actively change the settings area unless a preset is selected. The original reasoning is that a brush engine is a category/filter of a brush preset, not a brush itself. The current work around is to apply this patch that allows for this brush engine settings behavior to function closer to how it did in 3.x
The patch created other issues, so it could not be merged into master
The goal of this is to come up with a good solution for generating "the first preset" for an engine. This will mostly be useful for developers...so we might not want to call it out too much