Hello Joerg,

for the time being, we do not have ETA for this feature, as the demand for it is not very high as well as it would require some major changes in RadRichTextEditor control, to make it work as element, so it can be used in other control (like RadGridView). 

Furthermore, RadRichTextEditor is quite complex control with many layouts in it, hence it may not be performing very well in a grid control where cells are being constantly reused. 

I would suggest that you contact our support team to discuss your precise case, so they can see if we can help with something.