In Project Server / Project Online lookup tables, if you add a text lookup entry which contains a comma ‘,’ as such:
A validation message will appear on Project Server to say:
The lookup table values cannot contain the server list separator ‘,’ because, in multiple value fields, the entries are separated by a comma, hence a comma in the value is identified as a reserved character.
A simple way to work around this problem is to replace the comma in values with a comma look-a-like ASCII character ‚ This character looks like a normal comma but it is actually a different ASCII character with HTML Code ‚
Note: You can copy the comma in bold and paste it in your text.
A full list of Ascii characters can be found at this link http://www.ascii.cl/htmlcodes.htm
Once the comma is replaced with this character, the project server will let you save the lookup table. The comma look-a-like then will be visible when the user expands the drop down as shown below: