[Plugin] Access TV values on OnBeforeDocFormSave

Hi,

I need to get a TV value in a plugin running on the OnBeforeDocFormSave event. Since the resource id is 0 for new resources, I cannot access the TV via the id.
The documentation says using TVs on this event is complicated, however it does not say it is impossible https://docs.modx.com/revolution/2.x/developing-in-modx/basic-development/plugins/system-events/onbeforedocformsave
Using the OnDocFormSave is not an option in my case, unfortunately.

It seems there was a way to do this in evo https://forums.modx.com/thread/35173/tmplvars-on-onbeforedocformsave but I am not sure how to do this in Revo 2.5

Any ideas?

Best regards

Here is a stackoverflow post describing how it works in evo: http://stackoverflow.com/questions/7260155/modx-evolution-how-to-access-and-modify-a-template-variable-tv-before-save

According to this post, the $scriptProperties['data']['tvName'] should contain the data, but it seems the $scriptProperties['data'] array is empty

https://forums.modx.com/thread/86154/compare-tv-before-and-after-document-was-saved