I created a test case for creating a support ticket. Our support ticket interface has multiple tinymce editors present for the various ticket description and action update fields. I had a difficult time find a solution that would make Selenium IDE type text into one of these tinymce editors, but I found one that worked using the dom. Use command “type” and target should be “dom=document.getElementById(‘id_of_the_tinymce_frame’).contentDocument.body” and the value can be any text you want entered into the tinymce editor.
Note – if you copy and paste the dom code above, you may have to redo the single quotes around the id after you paste it somewhere else. I did this and the character changed and threw me off for a bit.