Merge elements

How are you? Hope you are doing awesome!

I have a question regarding the merge elements function. When using it, only frame elements can be merged, but Planar and Solid cannot as shown below. Is there a particular reason why the last two are hidden? 

How would you recommend merging walls or merging plates? Do we always have to regenerate those elements? Please let me know.

Thank you very much! 

Best regards,

Gen is software with the element-based modeling environment and there is no geometry in it. Merging surfaces or solids are only possible with the geometry which is just the object for the drawing. However, it is not possible with the FEM elements in which only three or four node plate element can be used and only 5, 6, 8 node solid element can be used.

In midas Gen, we should regenerate elements in order merge walls or plates.    

Regards,
DK Lee