The FAA claims they do not support filing delays within the US National Airspace System. This is from their ICAO interface document:
"The FAA currently has no requirements for any information to be filed in DLE/.
The FAA can accept DLE/ information, but it is not processed or presented to controllers. Do not use DLE for fixes in U.S. airspace at this time."
A method not currently supported by Leidos is to add a delay into your route as "Fix/Dh+mm." Here is an example indicating a 35 minute delay at SKIDS:
Your best option when using ForeFlight Mobile to file is to add delay information to the 'Remarks' to reflect that you plan to delay at a fix. For example, you could enter:
Delay 35 minutes at SKIDS
Once airborne, make sure the controller knows what your intentions are.