Add this you the Special configuration textarea for the multiline text field in the vLookup config (in the ViewFields section):
{"function":"readMore"}
Then add this to your Custom JS (in all forms and also in the list view if you use vLookup in a list view):
function readMore(val, item) {
var v = val;
if (val.length > 100) {
var trunc = val.substring(0, 100);
v = "<span style='cursor:pointer;' onclick='jQuery(this).hide().next().show()'>" + trunc + "...</span><span style='display:none;'>" + val + "</span>";
}
return v;
}
Please note that this will only work for a plain text multiline and not rich text (because the substring will break the HTML of the field value).
Alexander