Spell Check button not available in translated ZWC

[kratochvil]

Hi, I have ZCE 8.8.15 and after I add community translation (cs) I see no Check spelling button (nor Alt+X works). In other languages it works. So it must be enabled somewhere? The spell engine works (I installed custom cs dictionaries), because if I check mandatory check before sending email, it works as expected...
Can you please help me, where to enable the functionality in TinyMCE editor?
Thank you Jan