OK...well thought I'd post the code here in case anyone wants to do it the way I was talking about.
This only requires 4 lines of code...adding one line to 3 files and changing one line in another file.
This is for Roundcube 0.4 stable.
Open .\skins\default\templates\mail.html and go to around line 128.
Find:
<roundcube:button name="messagemenulink" id="messagemenulink" type="link" class="button messagemenu" title="messageactions" onclick="rcmail_ui.show_popup('messagemenu');return false" content=" " />
Add after:
<div style="float:left; clear:left; margin:-5px 0 0 0; font-size:10px; color:#666;">Check Create Reply Reply All Forward Delete Spam Mark More...</div>
Open .\skins\default\templates\message.html and go to around line 29.
Find:
roundcube:object name="mailboxlist" type="select" noSelection="moveto" maxlength="25" onchange="rcmail.command('moveto', this.options[this.selectedIndex].value)" class="mboxlist" />
Add after:
<div style="float:left; clear:left; margin:-5px 0 0 46px; font-size:10px; color:#666;">Create Reply Reply All Forward Delete Spam More...</div>
Open .\skins\default\templates\compose.html and go to around line 31.
Find:
<roundcube:button name="messageoptions" id="composemenulink" type="link" class="button messagemenu" title="messageoptions" onclick="rcmail_ui.show_popup('composemenu', true);return false" content=" " />
Add after:
<div style="float:left; clear:left; margin:-5px 0 0 52px; font-size:10px; color:#666;">Send Spell Attach Signature Save More...</div>
Open .\skins\default\mail.css and go to around line 30.
Find:
margin-right: 10px;
Replace with:
margin-right: 18px;
I've tested the above in FF 3.2.8, IE 8 and Opera 10.61 and all appears to be correct minus the spacing between the Spam and Mark button. A better way to do this would be to eliminate the all the all together an put each text in it's own element.