найти значение lookupcombobox properties listcolumns

Fig.1. Get choices from an external data source (in Drop-Down List Box Properties). I've used here as datasource the Title field of another (could be the same) sharepoint list called Dropdown

If you want to change choices without changing the template then you should define choices outside of the template itself. So change (in Drop Down List Box Properties) the List Box Choices from "Enter choices manually" to "Get Choices from an external data source" having configured the "Data Source:" (Add... button). One of the easy variants is to create and use a sharepoint list column (in another or the same sharepoint list) for this.

One should update template on Sharepoint server to make its changes visible/available to Sharepoint, i.e through Infopath Form Web Part.

I first need to republish the InfoPath to make it visible. Is there an other way?

When add a new choice value it won't be visible to the infopath webpart form. I've i don't use the infopath webpart form, it show all(incl the new adde value). The only solution that i found is to republish the infopath form.

I have a list with a column that accepts multiple values (a "choice" type with dropdown) and wish to add new choice options thats is available on an InfoPath(2010) webpart form.

I made a custom list in SharePoint(2010) and then created an infopath form based on that list. I created a new page in my SharePoint publishing site and added an infopath webpart that looked at my list/form. Everything works great.

infopath - SharePoint List form (add new choice value in dropdown) - SharePoint