WorkFlow Issues: Appending (not replace) Attendee Field in Calendar List and Email Variables (including .ICS file link)

Question

Kind of new to attempting any custom development in SharePoint.  Working with 2013 and have the 2013 Workflow Farm setup/working.  I am trying to have a calendar that users can register to appointments via custom list.  I
have the list that pulls the title into its  own "Event" field as a lookup.  Also have a workflow on the calendar that adds the current user as an attendee and made that field "not required".  I'm trying to accomplish this:
1) Have the Custom List update the Calendar list attendee field with the username. Currently it wipes out what is there and replaces with the "Created By" name. Tried to set a variable that would put the current attendees in a string
and just add the current user, then use that variable to update the attendee field.  No luck.  Ultimately if I can understand this enough and get fancy enough, I'd setup a workflow  that can have someone delete their own registration item in
the custom list and remove only their own name from Attendees...
2)  Have a workflow kick off an email that sends the registrant the calendar details. Have tried to pipe in variables to get the ICS file (some variation of this )
 If I put the List ID in brackets I get an error about having that and variables in the same code for an email workflow.  In any event I can't really get the email workflow to give any kind of nice piped in values the best looked like this and had
the wrong date: You registered for  {"results":[{"Id":22,"Value":"Test Event 8"}]} on 1/1/0001 12:00:00 AM

Answer 1

Hi Jason,
seems your requirement a bit complex, we forum team may have limited resource regarding this issue.
you may consider to use infopath for example from this 3rd party article:
http://www.bizsupportonline.net/infopath2007/programmatically-add-item-sharepoint-calendar-infopath.htm
or for general example:
http://office.microsoft.com/en-001/infopath-help/customize-a-sharepoint-list-form-HA101821257.aspx
the article is to add an item to your calendar list, so then you may need to do wipe or other procedures, by infopath you may add the data as
you need.
if should infopath feature may not be possible to use in your environment, i may need to suggest you to open an advisory case to us, by contacting our representative,
https://support.microsoft.com/
Regards,
Aries
Microsoft Online Community Support
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