Hi Raquel,
We would like to inform you that we don’t have this feature (“Justify the text in TextBox”) in ReportDesigner currently and so have logged feature report regarding this. A support incident to track the status of this feature has been created under your account. Please log on to our support website to check for further updates.
https://www.syncfusion.com/account/login?ReturnUrl=%2fsupport%2fdirecttrac%2fincidents
Please let me know if you have any questions.
Anandakumar S