Power BI Designer has been replaced by Power BI Desktop. Power BI Designer was the preview edition; Power BI Desktop is the GA release.
You can download the latest version here:
<span style=”color: #be9a27;”>https://powerbi.com/dashboards/downloads/designer</span>
Regarding your question, one of the itemized features in the latest release (July 24) is:
<b>Report Authoring Improvements</b>: New visualizations (Area Chart, Waterfall, Donut & Matrix); New visual formatting and customization options (labels, titles, background, legend, colors, etc.); Insert Textbox and Picture in your report; Support for hyperlinks in reports and report tables; Undo/Redo actions.
Hopefully the report authoring improvements include formatting number values.