Generators priority with `mps.lang.editor` when implementing custom CellModel

Hi!

I want to implement custom `CellModel` to use in my language's editor. So I created additional language `myLanguage.util` where I have created new concept `CellModel_DynamicList`. I've used `CellModel_RefNodeList` as example, so my concept:

1. Extends `CellModel_ListWithRole`
2. Declares template `reduce_CellModel_DynamicList` (which uses `cellFactoryMethod` mapping label, and produces an instance factory method for `EditorCell`)
3. Declares template `reduce_DynamicList_ListHandler` (which uses `nodeListHandler` mapping label, and produces private static class that extends `RefNodeListHandler`)

On this picture you can see that its reduction remplate is almost a copy of the template for `CellModel_RefNodeList`.
This reduction is the only one declared in the mapping configuration `editor_ext`, which is placed in my `myLanguage.util` language.
So I want for it to be generated equally with the `mps.lang.editor` templates.

In my language I already have created a cell of this custom type, and it looks like this:

But when I try to generate this editor, I managed to get three unworking possible results:

1. If I set generators priority: `myLanguage.util/main.editor_ext = jetbrains.mps.lang.editor/`

I get error messages:

```
Conflicting mapping priority rules encountered:
Coherent configurations with different 'top priority' setting: [myLanguage.util/:myLanguage.util.generator.template.main.editor_ext] strictly_together [jetbrains.mps.lang.editor/:*]
```

2. If I set generators priority: `myLanguage.util/main.editor_ext >= jetbrains.mps.lang.editor/`

I get error messages:

```
Conflicting mapping priority rules encountered: Configuration with lower priority blocks high-priority configuration: [myLanguage.util/:myLanguage.util.generator.template.main.editor_ext] after_or_together [jetbrains.mps.lang.editor/:*]
```

3. If I set generators priority: `myLanguage.util/main.editor_ext <= jetbrains.mps.lang.editor/`

I get errors:

```
broken reference 'baseMethodDeclaration' in [operation] InstanceMethodCallOperation null[3044460634876100567] in myLanguage.editor@20_0 (target model is null)
-- -- was input node: [operation] InstanceMethodCallOperation null[3044460634876100567] in myLanguage.editor@20_0
broken reference 'baseMethodDeclaration' in [operation] InstanceMethodCallOperation null[3044460634876100578] in myLanguage.editor@20_0 (target model is null)
-- -- was input node: [operation] InstanceMethodCallOperation null[3044460634876100578] in myLanguage.editor@20_0
```
And these errors are the interesting ones, cuz as you can see on the previous picture my editor page contains an `indent collection` with two child elements: a constant cell, and my custom dynamic list cell.

Errors point to this transient model page:

As you can see - it contains private instance method `createDynamicList_` and private static class `DynamicListHandler_`, and both of them are produced by my custom cell model.

Method `createDynamicList_` properly references static class thru `nodeListHandler` mapping label.

But `createCollection_` method indicates two errors:

1. It tries to call method `createDynamicList_` twice, even though there's only one cell node of this type in the editor.

2. It fails to call method `createDynamicList_`, even thou by default it uses `template_CreateCellExpression` (from `mps.lang.editor`) which uses mapping label `cellFactoryMethod` to generate proper factory method call, and reduction of my cell model DOES use the same mapping label to produce instance factory method:

I am trying to find a solution for a day now, but it seems I just don't get it. My generators priority looks like this:

What is the proper way to configure generators priority in such a case?

Or is there another way to make it work?

Greatest thanks in advance!