I discussed this issue with the team to increase its priority and we moved the it to a planned stage.
The item will be directly updated when there is any progress on it, you can track it here:
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Thank you for reporting this.Until this is resolved, this article can be used to make a custom format tool and add the missing attribute:https://www.telerik.com/kendo-react-ui/knowledge-base/add-custom-tools-to-the-editor-and-customize-built-in-tools/#toc-apply-custom-fontsize
Additionally, I have added some Telerik points to your account for bringing this to our attention.Apologies for the inconvenience this may have caused you.