Yep this is a doable but is done via the presentation layer in vRO.

You shound never use the XaaS form editor in vRA as it is rubbish and everytime you need to refresh the form you need to make all your changes again. if all the smarts are in the presentation layer most will surface up into vRA, This is how you can hide tabs or populate drop downs with actions using OGNL. And it is much much faster to load the forms. I have done a couple videos on my vblog in regards to xaas and vra https://www.youtube.com/channel/UCWfyTiUBwRKjB_qckVPVpcQ