Scenario is: I have a user task form, which has a search button. On click of whi

You can do it as follows.
Step 1. User search screen. This will show the search options and section to show the selected search result record (initially all blank). If you want, you can hide this by putting this in a section
Step 2 - This will show the search result. You will have a script task inbetween doing the search bit.
Step 3 - Once user selects the desired record from the previous step, Select the info of the selected record and populate the form from STEP 1.
Step 4 - Activity chain all these forms. Once done, they will appear as a seamless flow of events.

Hi Sathya, thanks for your reply. The first form is not only a search screen, it has multiple data to be entered. While user is entering data, the user has option to search for "Events" and "Third Party Company Details" in the first form. So the first form needs to remain visible while he can search on second screen.

Harish, irrespective of what the form is, the solution would remain the same. You need to ensure that whenver you step out of the form to do a search and come back again, you fill the form with the default value of what the user had entered in the 'other' sections of the form. Save the value into PV and use them as default value for these fields. This should do the job.

Thnks Sathay, however, I would require more clarifications to understand.

First let me be more clear in what is the requirement; as an example: The "Input Form" has fields like Name, Date, Events. Events field data is in DB. The Input Form has a search button next to Events field. On click of the search button, a new Search Form should open however, the Input Form should be active for further data inputs as well. On the new Search Form, whatever user searches and selects, need to be displayed in a grid form in the Input Form.

I am not sure of how to achieve this with activity chaining or using quick tasks. Particularly while I come back, how will I update an active visible task window?

Harish, I understand what your requirements are. The only difference here is that when you move from the Input form to Search screen, the input form will not be there in the background. The search screen will open as the next step in the process, collect the data and then it will loop back to the Input form, at which stage, you will have the record selected from the search result.
See
forum.appian.com/.../Activity-Chaining_from_a_Start_Form
and
forum.appian.com/.../Configuring_Activity-Chaining

Thanks Sathya