Comprehensive theme editor is required for Desktop
Report themes are great. For quite some time we have been able to build JSON file that describe themes. At first they were relatively simple, but have evolved to include theming options for virtually every aspect of a report.
The September 2019 edition of Power BI Desktop introduces a massive number of additions to theming. There are now so many that simple, textual JSON file editing is now impractical. We NEED a graphical theme editor.
Power BI Desktop itself could act as the editor with one simple feature addition. Export current visual settings to a theme file (JSON). With that, Desktop could be used to get things "just so" and then save out the JSON for re-use.
This item rolls up a couple of other ideas:
Richard Thorek commented
Suggestion for implementation consideration. Ability to import / use theme files from other office apps to bring consistency in a corporate setting. Even as a starting point before additional customisation.