[marinew]

I found the code to modify in order to reduce minimal size of appointments :
In /opt/zimbra/tomcat/webapps/zimbra/js/ZimbraMail_all.js at line 33633 (for Zimbra 4.5)

ZmCalColView.prototype._getBoundsForDate=function(d,_2091,col){
var _2093=_2091/1000/60;
// Old value :
// _2093=Math.max(_2093,22);
// New value :
_2093=Math.max(_2093,11);
var h=d.getHours();
var m=d.getMinutes();
if(col==null&&!this._scheduleMode){
var day=this._getDayForDate(d);
col=day?this._columns[day.index]:null;
}
(...)
ZmCalColView.prototype._getBoundsForCalendar=function(d,_2098,_2099){
var _209a=_2098/1000/60;
// Old value :
// _209a=Math.max(_209a,22);
// New value :
_209a=Math.max(_209a,11);
var h=d.getHours();
var m=d.getMinutes();
var col=this._getColForFolderId(_2099);
if(col==null){
return null;
}

There remains a problem : the vertical bar displaying busy state in "Programme" (in french) view does not show 10 minutes free places.
No time to look at this now...