Idea, not well worked out yet: I can imagine that theme developer can include/exclude question types/question themes in some way. For example: exclude array questions from mobile only theme.

I'm unsure on this point .
Example

• Button : it's a question type for single choice, but an attribute for YesNo and gender. I think here : Theme as attribute is OK
• Checkbox for Array number : clearly must be a theme separate as Question type
• https://gitlab.com/SondagesPro/QuestionTheme/arraytext_display_rows : I think it's best if it's stay a QuestionTheme and not a Question Type
• https://gitlab.com/SondagesPro/QuestionTheme/really_hidden_equation : I think it's best if it's stay a QuestionTheme and not a Question Type
• https://gitlab.com/SondagesPro/QuestionTheme/EmailInput QuestionTyep OK ONLY when we can add validation Expression in QuestionTheme

Overall, makes sense but I would like to see an indication of what is core and what is custom.

Another Example (with Slider of Tony )
Slider question is a settings of Multi numeric
But 2 specific slider is new Question type https://github.com/tpartner/LimeSurvey-Slider-Controls-3x

Since Theme dev can choose to be in dropdown or in Theme chooser : why change tis ? Realy needed ? If it's for more stability OK.
But if you think it's for user : i really think it's false. I can be more complicated for some user (and less unerstandable).

Merged into develop.