Hi Paul,
We have analyzed your requirement and we are unable to
change the size of the BackStageButton in our current implementation.
We have logged this as a feature, it will be included in any of our
upcoming releases.
Please log on to our support website to check for further
updates.
https://www.syncfusion.com/account/login?ReturnUrl=%2fsupport%2fdirecttrac%2fincidents
Please let us know if you have any further assistance.
Regards,
Jegan Raj M