As of WorkWithPlus for Web 14, the use of DVelop Combos in grids is allowed.

In order to implement it, you do the same thing you have been doing outside the grid:

For example, if we have a Country transaction that has many cities, the cities are loaded with a grid, and you can do it in the following way:

It is important to note that all the properties of the DVelop Combo apply in this case as well.