Do you have Nintex Workflow? Using a workflow to update or create item in the second list is the easiest way I can think of.

Hi Vlad,

If you have the Forms Enterprise license you will be able to do a web call  from form A to get information from form B.

If you don't have enterprise license you will have to use a the lookup listview and filter on some of the options in Form A to pull the information from Form B into the List View.

Let me know if you need more information regarding this.

would you mind to share what exactly you would like to do from logical point of view?

I have a list A and from its start form I need call  start form of list B.

sharepoint list doesn't have any start form. you can create a form to create/edit/view a list item, but it doesn't start anything (I do omit any javascript  hardcoding).

next, you can define a workflow on a list or on a workflow on a site. both of them can have defined its own start form.

so, your description seems to mix two different thing to me.

please clarify what exactly do you mean.

once you sort out the above questioned, please clarify  what's your  logical/business requirement to link the two lists.

possibly, there are some other (easier, proven...) ways  how to achieve that apart from some strange forms mutual interlinks.

Hello everybody! 
Thanks for your answers!
Yes, I have Enterprise License for Nintex FW and Forms 2013, but I am use it only for a month and have created only 3 WF . I will try to explain what I need.

For Example, I have List A and List B. I can save ID of List A item in the column of list B item to bound this lists. However, how can I fill new item of list B from new item Nintex form of the list A? May be duplicate unbound fields for list B in form A, then create List B item with "Create item in another list" Action?.. List B have columns of type Choice…. As I understand now, SP Choice is not good idea... It is better to user separate lists for each lookup value instead of SP choices…. In this case I don’t need duplicate choices list in form A for list B, but I can in unbound filed in Form A for list B use the same lookup values and then create new item in list B. Sounds good until you need update item in list A and show bound list B item for editing…. May be I on the half of the road, maybe I am on wrong road :-)

still quite hard to understand what you really need.

I would once again encourage you to describe your logical case (like I have orders in list A and order items in list B and I want to enter both from one form). maybe someone will come up with much easier solution then you are trying to implement.

if you posted examples/screenshots it might be helpfull as well.

I will try to answer what I think I understood.

I can save ID of List A item in the column of list B item to bound this lists

how do you do that?

if you are able to do it for one field you should be able to do it the same way for the other as well.

how can I fill new item of list B from new item Nintex form of the list A

you can not do it (directly).

the form is always bound to single list so it can access just field of that list.

if you need users enters data on one place/form, you can imitate it so that you first store all the data to one list and then do some post-processing that copies/moves part of data to another list. the post-processing is typically done by a workflow.

then create List B item with "Create item in another list" Action

here you already speak about workflow action. it is not available in forms.

List B have columns of type Choice…. As I understand now, SP Choice is not good idea... It is better to user separate lists for each lookup value instead of SP choices…. In this case I don’t need duplicate choices list in form A for list B, but I can in unbound filed in Form A for list B use the same lookup values and then create new item in list B.

this is a but messy for me, not clear what you want to achieve...

choice fields make sense in some circumstances. in other scenarios it's better to use lookups.

if you need to refernce the same list of option from both lists then probably a lookup will be better for you.

Sounds good until you need update item in list A and show bound list B item for editing

that's always drawback of keeping the same data at several places and need to keep them in sync.you should ask yourself as well what should happen if data are changed in listB and you will need them to sync into listA.