I support this!

It's been an issue for a long time - also before the new schema validation. Would be super nice with a fix :)

Some nitty gritty details from my experience:

(FYI: I am using schema 2.117, since I am on Report Server May 2023.)

1) When using Dropdown in the theme file

This actually kinda works, but you have to manually click "Reset to default" in the menu after creating the slicer in Desktop. Of course this defeats the point of a default setting.

So part of the issue seems to be that, when we as users create a slicer, it is pre-set with a value that overrides the theme file from the start - in the same way as if we had changed the property manually.

2) When using HorizontalList or VerticalList in the theme file

Both don't really work at all. The behavior in Desktop is a bit complicated:

1. A newly created slicer defaults to VerticalList.
2. When choosing either VerticalList or HorizontalList and then clicking "Reset to default" the slicer doesn't change - thus ignoring the value in the theme file.
3. When choosing Dropdown and then clicking "Reset to default" the slicer reverts to whichever of the above was last chosen - effectively still ignoring the value in the theme file.

3) When using a Date or Time related mode in the theme file

These work exactly the same way as setting mode to Dropdown in the theme file.

🙏🏻 I hope these details can help resolve the issue.

from powerbi-desktop-samples.

I'm surprised that this hasn't been fixed or even commented on as to why.
This is one of the most used visuals, it's very disheartening when I have to say to customers,
"Here's your theme file to give you consistent report design across your org. Sorry, no, I can't set that to default to dropdown, it's a limitation of the product".

from powerbi-desktop-samples.

Just read the ReadMe in detail so tagging as requested. @yelper

from powerbi-desktop-samples.