I tried that at first, but it results in a weird behaviour where the text marker in the input jumps to 0,0 and if you start typing after the form success (without first clicking inside the textarea) a line break will be inserted below the first text row. Not sure what’s up with that, but feeding it the var’s empty value does not result in that behaviour.
If you want to reproduce it.
This is the textArea
<textarea id="editor_new_note" is="dmx-medium-editor" style="border-radius: 5px; width: 100%; outline: none !important; padding: 15px; font-size: 13px; overflow: scroll; height: 110px;" placeholder="" buttons="bold,italic,underline,strikethrough,orderedlist,unorderedlist,removeFormat" auto-link="true" auto-list="true" target-blank="true" align="left" fontawesome="true" name="description" required="" data-msg-required="" disable-extra-spaces="true"></textarea>
on form success
editor_new_note.setValue('')