Here is a list of limitations I encountered with Cassandra: 

1) In ER Modeler, not all data types are present. I.E. "date" is missing 
2) In ER Modeler and the main ADS application, I cannot create or see User Defined Types... As a result, new columns/tables cannot be created through the UI which use UDTs 
3) When querying tables that have UDT columns , the results are no shown. This column is a: list<frozen<udt>> and it shows as: 'java.nio.HeapByteBuffer[pos=173 lim=229 cap=8293730]' 
4) In ER Modeler, there is no option for a frozen column 
5) In ER Modeler, when setting the Primary key, which in Cassandra is a mix of those that are partition key, and sequence columns, it's, awkward and just not working. I cannot seem to make it work at all actually - it's ignoring the column parameter when I set it to true - and the clustering order value in storage is not doing the right thing in the create table script. 

All in all the ER Modeler, other than create a visual picture of the db I want to create, it's prtty much useless. I have to finish off the create table script by hand. 

I am using version 9.5 btw.