Thank you for using EmEditor!
Which toolbar button are you talking about? There are no spelling checker buttons yet in the current version (beta 6). I suppose you are using a Plug-in spelling checker. The plug-in spelling checker is completely different from the new spelling checker. So you should uninstall the old plug-in spelling checker.
“Add to Dictionary” command is already included in the context menu. “Ignore” and “Ignore All” are not (same as FireFox). I might consider those Ignore commands in future versions.
Please let me know if you have further questions.